Ethiopian Environmental Health University Exit Exam Practice Questions (50 Items)

Thematic Area 1: Water Quality and Supply Management

Q1. In a rural Ethiopian community, a slow sand filter is being constructed to treat surface water. What is the primary mechanism responsible for the removal of pathogenic bacteria and organic matter in the top layer of this filter? A) Mechanical straining by coarse gravel layers B) Biological action within the Schmutzdecke layer C) Chemical precipitation using aluminum sulfate D) Rapid backwashing using pressurized air

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• Correct Answer: B
• Rationale: The Schmutzdecke (zoogleal layer) is a complex biological layer formed on the surface of slow sand filters that actively degrades organic matter and destroys pathogens through predation and adsorption.

Q2. During a routine water quality assessment of a municipal water supply system, an Environmental Health Technician detects a high level of fecal coliforms. What does the presence of fecal coliforms primarily indicate? A) The water is highly acidic and corrosive to pipes B) The water has been contaminated with human or animal excreta C) Toxic heavy metals have leaked into the reservoir D) Industrial chemical runoff is present in the water system

• Correct Answer: B
• Rationale: Fecal coliforms, particularly Escherichia coli, serve as specific indicator organisms denoting recent contamination by warm-blooded animal or human feces and the potential presence of enteric pathogens.

Q3. Which of the following water treatment processes is specifically designed to remove dissolved gases, volatile organic compounds (VOCs), and oxidize dissolved iron and manganese? A) Coagulation B) Sedimentation C) Aeration D) Flocculation

• Correct Answer: C
• Rationale: Aeration physicalizes intimate contact between water and air, which strips volatile gases (like H2​S) and introduces oxygen to precipitate soluble iron and manganese into filterable solids.

Q4. To ensure effective disinfection of community drinking water using chlorine, what is the standard recommended minimum residual chlorine concentration and minimum contact time required at the point of delivery? A) 0.1 mg/L for 10 minutes B) 0.5 mg/L for 30 minutes C) 2.0 mg/L for 5 minutes D) 5.0 mg/L for 60 minutes

• Correct Answer: B
• Rationale: WHO guidelines recommend a free residual chlorine concentration of ≥0.5 mg/L after at least 30 minutes of contact time at pH <8.0 to ensure proper disinfection throughout distribution systems.

Q5. A groundwater sample from the Ethiopian Rift Valley region shows a fluoride concentration of 6.5 mg/L. What is the most likely public health consequence among children who consume this water over a prolonged period? A) Blue baby syndrome (Methemoglobinemia) B) Severe dental and skeletal fluorosis C) Goiter and iodine deficiency disorders D) Acute bacillary dysentery

• Correct Answer: B
• Rationale: Chronic ingestion of water with fluoride concentrations exceeding the optimum level (typically >1.5 mg/L) leads to structural defects in teeth (dental fluorosis) and severe bone abnormalities (skeletal fluorosis).

Q6. Which parameter is classified as a physical characteristic of drinking water quality? A) Dissolved Oxygen (DO) B) Total Dissolved Solids (TDS) C) Turbidity D) Nitrate concentration

• Correct Answer: C
• Rationale: Turbidity measures the clarity or cloudiness of water caused by suspended particles, which is a physical properties observation.

Q7. In the coagulation process of water treatment, what is the primary role of adding chemical coagulants like alum (Aluminum Sulfate)? A) To directly kill enteric viruses and protozoan cysts B) To neutralize the negative electrical charges on suspended colloidal particles C) To increase the hardness and mineral content of soft water D) To lower the pH of water to make it more alkaline

• Correct Answer: B
• Rationale: Colloidal particles in water carry negative charges that repel each other. Alum provides positively charged trivalent aluminum ions that neutralize these charges, allowing particles to coalesce.

Q8. Which water-related disease mechanism best classifies Schistosomiasis (Bilharzia), where the pathogenic parasite requires an aquatic intermediate snail host to complete its lifecycle before infecting humans via skin penetration? A) Water-borne disease B) Water-washed disease C) Water-based disease D) Water-related insect vector disease

• Correct Answer: C
• Rationale: Water-based diseases are caused by aquatic organisms or parasitic worms that spend part of their life cycle in intermediate aquatic hosts before infecting humans through contact with water.

Q9. When selecting a site for digging a shallow hand-dug well in a rural village, what is the minimum standard horizontal distance that must be maintained from a pit latrine to prevent microbial cross-contamination? A) 5 meters B) 15 meters C) 30 meters D) 100 meters

• Correct Answer: C
• Rationale: Standard environmental health guidelines dictate a minimum safe distance of 30 meters between a water source and a localized subsurface sanitation facility like a pit latrine.

Q10. A water quality test shows an elevated level of nitrates (55 mg/L) in a shallow well located near an agricultural field. Infants consuming formula prepared with this water are at high risk for developing: A) Minamata disease B) Typhoid fever C) Methemoglobinemia D) Fluorosis

• Correct Answer: C
• Rationale: High nitrate intake in infants is reduced to nitrite in the digestive tract, which binds to hemoglobin to form methemoglobin, reducing the blood’s oxygen-carrying capacity and causing “blue baby syndrome.”

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Thematic Area 2: Liquid Waste Management

Q11. In a standard municipal wastewater treatment plant, what is the primary objective of the secondary treatment stage? A) Physical removal of large floating debris using screens B) Biological degradation of dissolved organic matter using microorganisms C) Chemical precipitation of heavy metals and phosphorus D) Disinfection of effluent using ultraviolet light

• Correct Answer: B
• Rationale: Secondary wastewater treatment uses biological processes (such as activated sludge or trickling filters) where aerobic microorganisms consume dissolved and colloidal organic matter, measured as Biochemical Oxygen Demand (BOD).

Q12. What does a high Biochemical Oxygen Demand (BOD) value in a river water sample downstream from a textile factory indicate? A) The water has a high concentration of dissolved oxygen available for fish B) There is a high load of organic pollution requiring large amounts of oxygen for decomposition C) The water is highly saline and clear of any bacterial contamination D) The temperature of the water is optimal for aquatic plant growth

• Correct Answer: B
• Rationale: BOD measures the amount of oxygen consumed by microorganisms while decomposing organic matter under aerobic conditions. High BOD indicates severe organic pollution and depleted oxygen levels for aquatic life.

Q13. In a suburban septic tank system, what is the purpose of the concrete baffles or tees located at the inlet and outlet pipes? A) To accelerate the flow of raw sewage into the drainage field B) To prevent the scum layer from escaping into the absorption trench or drainage field C) To aerate the sewage and provide oxygen to anaerobic bacteria D) To chemically treat the incoming pathogenic organisms

• Correct Answer: B
• Rationale: Baffles slow the flow of wastewater and prevent scum (floating oil/grease) and sludge solids from leaving the tank and clogging the pores of the soil absorption or drainage field.

Q14. Which stabilization pond type in a waste stabilization pond system is specifically designed to be deep (2–5 meters) and relies entirely on anaerobic bacteria to break down heavy organic loads without any dissolved oxygen? A) Maturation pond B) Facultative pond C) Anaerobic pond D) Aerated lagoon

• Correct Answer: C
• Rationale: Anaerobic ponds are deep, un-aerated structures designed to receive high organic loads, where anaerobic bacteria digest settled solids in the complete absence of dissolved oxygen.

Q15. The ecological process where an excess of nutrients (such as nitrogen and phosphorus from raw sewage discharge) causes rapid algal blooms, leading to oxygen depletion and the death of aquatic life in a lake is known as: A) Biomagnification B) Eutrophication C) Bioaccumulation D) Salinization

• Correct Answer: B
• Rationale: Eutrophication is the nutrient enrichment of water bodies, triggering excessive plant and algal growth. When these plants die and decompose, the process consumes oxygen, killing fish and aquatic organisms.

Q16. Which system is classified as an “on-site sanitation system” for liquid waste management? A) Conventional gravity sewerage system B) Ventilated Improved Pit (VIP) Latrine C) Activated sludge treatment facility D) Up-flow Anaerobic Sludge Blanket (UASB) reactor

• Correct Answer: B
• Rationale: On-site systems treat and dispose of waste at the location where it is generated. VIP latrines are a classic example of dry, localized on-site sanitation.

Q17. What is the main function of the vent pipe equipped with a fly-proof mesh screen in a Ventilated Improved Pit (VIP) Latrine? A) To provide light inside the superstructure squatting area B) To create a continuous draft of air that minimizes odors and traps exiting flies in the vent pipe C) To drain rainwater away from the pit foundation D) To allow easy mechanical emptying of fecal sludge

• Correct Answer: B
• Rationale: The vent pipe absorbs solar heat and creates an updraft, pulling odors out of the pit. Flies are attracted to the light at the top of the pipe, where they are trapped and die against the mesh screen.

Q18. In the activated sludge process, what is the purpose of returning a portion of the settled sludge from the final clarifier back into the aeration tank (Return Activated Sludge)? A) To dilute the incoming highly toxic industrial wastes B) To maintain a high concentration of active, acclimated microorganisms in the aeration basin C) To adjust the pH of the wastewater before chemical chlorination D) To reduce the operational electricity cost of the mechanical surface aerators

• Correct Answer: B
• Rationale: Returning settled sludge ensures that an optimal population of active biomass (mixed liquor volatile suspended solids) is available to continuously digest incoming raw organic waste.

Q19. What type of soil condition is considered most ideal for the installation of a septic tank soil absorption field (soak pit)? A) Impermeable solid bedrock B) Highly plastic dense clay soil with low permeability C) Moderately permeable sandy loam soil with a deep water table D) Saturated marshland soil with a high water table

• Correct Answer: C
• Rationale: Soil must have adequate percolation characteristics to absorb and filter effluent. Dense clay or high water tables lead to surface ponding and system failure.

Q20. Which parameter measures the total amount of chemically oxidizable matter in wastewater, using a strong chemical oxidant like potassium dichromate under acidic conditions? A) Total Suspended Solids (TSS) B) Chemical Oxygen Demand (COD) C) Biochemical Oxygen Demand (BOD) D) Total Organic Carbon (TOC)

• Correct Answer: B
• Rationale: COD measures the oxygen equivalent of the organic matter content susceptible to strong chemical oxidation, which captures both biodegradable and non-biodegradable organic matter.

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Thematic Area 3: Solid Waste Management

Q21. According to the Integrated Solid Waste Management (ISWM) hierarchy, which management strategy should be given the highest priority to minimize environmental impact? A) Sanitary landfilling B) Incineration with energy recovery C) Recycling and composting D) Source reduction and waste minimization

• Correct Answer: D
• Rationale: The ISWM hierarchy ranks strategies from most preferred to least preferred: Source reduction/prevention is the highest priority, followed by reuse, recycling, recovery, and lastly, disposal (landfilling).

Q22. What is the highly toxic, contaminated liquid that collects at the bottom of a solid waste dump site or landfill as a result of rainwater percolating through decomposing waste layers? A) Effluent B) Leachate C) Sludge D) Graywater

• Correct Answer: B
• Rationale: Leachate is formed when moisture flows through solid waste, extracting dissolved or suspended matter, chemicals, and heavy metals from the decomposing mass.

Q23. In an urban municipality, an Environmental Health Officer is designing a composting program for organic kitchen waste. Which optimal Carbon-to-Nitrogen (C:N) ratio must be maintained to foster rapid aerobic decomposition by microorganisms? A) 5:1 to 10:1 B) 25:1 to 30:1 C) 70:1 to 80:1 D) 100:1 to 150:1

• Correct Answer: B
• Rationale: Microorganisms need carbon for energy and nitrogen for protein synthesis. A C:N ratio of 25:1 to 30:1 provides the ideal nutrient balance for efficient aerobic composting.

Q24. Which gas is produced in the largest volume under anaerobic conditions inside a deep sanitary landfill, posing a significant risk of explosion if not properly vented? A) Carbon monoxide B) Hydrogen sulfide C) Methane D) Nitrogen dioxide

• Correct Answer: C
• Rationale: Anaerobic decomposition of organic waste in sealed landfills yields landfill gas, which is primarily composed of methane (∼50–60%) and carbon dioxide (∼40–50%).

Q25. Healthcare waste must be strictly segregated at the point of generation. According to standard international color-coding protocols, which type of waste must be placed inside a yellow plastic bag or container? A) Non-hazardous general municipal waste (e.g., paper, food peels) B) Infectious and anatomical hazardous wastes C) Radioactive waste materials from oncology units D) Non-infectious pharmaceutical packaging boxes

• Correct Answer: B
• Rationale: Yellow bags or containers are universally designated for infectious, biohazardous, and anatomical wastes requiring specific treatment like autoclaving or incineration.

Q26. What type of medical waste should always be disposed of inside a puncture-proof, leak-resistant “Sharps Box”? A) Used blood collection bags B) Expired multi-vitamin syrups C) Used hypodermic needles, scalpel blades, and broken glass vials D) Anatomical waste from the labor ward

• Correct Answer: C
• Rationale: Sharps containers prevent needle-stick injuries and accidental transmission of blood-borne pathogens among healthcare workers and waste handlers.

Q27. What is the primary operational purpose of applying a 15-to-20 cm layer of daily soil cover over compacted solid waste in a sanitary landfill? A) To increase the market value of the land for future agriculture B) To prevent vector breeding (flies, rodents), minimize odors, and control wind-blown litter C) To chemically neutralize hazardous heavy metal components D) To stop the generation of leachate and methane gas entirely

• Correct Answer: B
• Rationale: Daily soil compaction and coverage form a barrier that deters pests, controls odors, reduces fire risks, and prevents litter scatter.

Q28. Which solid waste disposal method utilizes controlled, high-temperature thermal combustion (>850∘C) to convert organic waste into ash and gaseous emissions? A) Open dumping B) Incineration C) Shredding D) Pyrolysis

• Correct Answer: B
• Rationale: Incineration is a thermal treatment process that combusts waste under controlled conditions, reducing its volume and mass while converting it to ash and flue gas.

Q29. Plastic wastes made of Polyvinyl Chloride (PVC) should not be burned in low-temperature open fires because their combustion releases which highly toxic, carcinogenic environmental pollutants? A) Carbon dioxide and water vapor B) Dioxins and Furans C) Methane and sulfur dioxide D) Nitrogen and argon gases

• Correct Answer: B
• Rationale: Open burning of chlorine-containing plastics like PVC at low temperatures generates polychlorinated dibenzo-p-dioxins (dioxins) and dibenzofurans, which are highly toxic carcinogens.

Q30. What type of waste collection system requires residents to carry their household waste containers to a specific, centrally located community container skip at scheduled times? A) Curb-side collection system B) Communal (block) collection system C) Door-to-door collection system D) Backyard collection system

• Correct Answer: B
• Rationale: In communal or block collection, residents bring their waste to fixed collection points or skips placed across neighborhoods, which is common in many urban centers.

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Thematic Area 4: Food Hygiene and Safety

Q31. An outbreak of foodborne illness occurs at a university cafeteria. Symptoms appear rapidly within 2 to 6 hours after individuals consumed a custard dessert, characterized by severe vomiting and abdominal cramps without fever. What is the likely causative organism? A) Salmonella typhi B) Staphylococcus aureus (enterotoxin) C) Vibrio cholerae D) Clostridium tetani

• Correct Answer: B
• Rationale: Staphylococcus aureus produces a heat-stable enterotoxin in food. It has a rapid onset of symptoms (1–6 hours) dominated by vomiting due to pre-formed toxins, without fever.

Q32. What is the primary objective of implementing the Hazard Analysis Critical Control Point (HACCP) system in a large-scale food processing factory? A) To inspect final products and penalize workers for defects B) To proactively identify, evaluate, and control significant food safety hazards at specific steps in production C) To maximize the financial profit margin of the food business D) To ensure that food labeling designs are aesthetically pleasing

• Correct Answer: B
• Rationale: HACCP is a preventive management system focused on identifying food safety hazards at specific points (Critical Control Points) in the production process to prevent contamination before it occurs.

Q33. To prevent the multiplication of pathogenic bacteria in perishable foods, what is the temperature range defined as the “Food Danger Zone”? A) −18∘C to 0∘C B) 5∘C to 60∘C C) 75∘C to 100∘C D) 121∘C to 135∘C

• Correct Answer: B
• Rationale: The danger zone (5∘C to 60∘C, or 40∘F to 140∘F) provides the ideal temperature conditions for rapid bacterial growth and replication.

Q34. Which food preservation technique involves heating milk to a specific temperature (e.g., 72∘C for 15 seconds) to destroy all pathogenic microorganisms without significantly altering the nutritional quality? A) Sterilization B) Pasteurization C) Autoclaving D) Fermentation

• Correct Answer: B
• Rationale: Pasteurization uses controlled heat to eliminate key pathogens (like Mycobacterium bovis and Coxiella burnetii) in milk without damaging its taste or nutritional structure.

Q35. A consumer develops severe paralysis, blurred vision, and respiratory difficulty 24 hours after eating home-canned vegetables. The toxin responsible blocks acetylcholine release at neuromuscular junctions. Which organism produces this toxin? A) Escherichia coli B) Clostridium botulinum C) Bacillus cereus D) Shigella dysenteriae

• Correct Answer: B
• Rationale: Clostridium botulinum is an anaerobic spore-former that produces botulinum neurotoxin in improperly processed anaerobic environments like home-canned goods, causing life-threatening flaccid paralysis.

Q36. Cross-contamination in a commercial kitchen can be effectively prevented by which of the following practices? A) Using the same wooden cutting board for raw chicken and ready-to-eat salad greens B) Storing raw meat packages directly above uncovered cooked rice bowls in the refrigerator C) Using separate, color-coded cutting boards and knives for raw meats and ready-to-eat foods D) Washing hands with cold water only once at the start of the morning shift

• Correct Answer: C
• Rationale: Color-coded equipment establishes a physical separation that prevents the transfer of pathogens from raw commodities to foods that will not undergo further cooking.

Q37. What type of foodborne hazard is represented by the presence of organophosphate pesticide residues on fresh tomatoes sold at a local market? A) Biological hazard B) Physical hazard C) Chemical hazard D) Ergonomic hazard

• Correct Answer: C
• Rationale: Pesticides, toxic heavy metals, cleaning agents, and food additives fall under chemical food safety hazards.

Q38. During an inspection of a butchery, an Environmental Health Officer notices that the cold storage room temperature is kept at 12∘C. What corrective action should be ordered immediately? A) Maintain the temperature since it is well within the acceptable zone B) Lower the cold storage room temperature to ≤4∘C immediately C) Increase the temperature to 25∘C to keep the meat dry D) Turn off the refrigerator at night to conserve municipal electricity

• Correct Answer: B
• Rationale: Raw meat must be refrigerated at or below 4∘C to retard bacterial growth and prevent spoilage.

Q39. Which organism is a major cause of foodborne bacterial infections linked to the consumption of undercooked poultry, raw milk, and contaminated water, often causing bloody diarrhea and abdominal pain? A) Campylobacter jejuni B) Lactobacillus acidophilus C) Saccharomyces cerevisiae D) Clostridium perfringens

• Correct Answer: A
• Rationale: Campylobacter jejuni is a common zoonotic bacterial pathogen found in poultry intestines; ingestion of undercooked poultry products causes campylobacteriosis.

Q40. What is the core definition of food adulteration? A) The intentional addition of synthetic vitamins to enhance nutritional profile B) The debasement of food quality by adding inferior, cheaper substances or removing valuable components for illicit financial gain C) The biological decomposition of food due to poor refrigeration D) Cooking food at temperatures exceeding 100∘C

• Correct Answer: B
• Rationale: Adulteration involves intentionally altering food composition by mixing cheaper additives or removing key ingredients, which degrades safety and quality for profit.

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Thematic Area 5: Institutional Health and Safety

Q41. When inspecting a primary school classroom, an Environmental Health Officer calculates the floor area to evaluate overcrowding. What is the minimum standard floor space required per student in a standard classroom setting? A) 0.2 m2 B) 1.2 m2 to 1.5 m2 C) 5.0 m2 D) 10.0 m2

• Correct Answer: B
• Rationale: Standard school health guidelines require approximately 1.2 to 1.5 m2 of floor area per student to ensure adequate spacing, reduce airborne transmission of diseases, and provide a conducive learning environment.

Q42. Which institutional setting carries the highest risk for the transmission of Nosocomial (healthcare-associated) Infections due to the concentration of susceptible, immunocompromised hosts? A) Public primary schools B) Municipal prison units C) Hospitals and health centers D) Central railway stations

• Correct Answer: C
• Rationale: Healthcare facilities concentrate vulnerable patients and invasive procedures, increasing the risk of nosocomial transmissions by pathogens like MRSA or Pseudomonas.

Q43. What is the primary environmental engineering intervention used to control airborne transmission of Mycobacterium tuberculosis within a crowded hospital waiting hall? A) Chemical spraying of the floor with chlorine solutions every hour B) Installation of adequate negative-pressure ventilation and maximizing natural cross-ventilation windows C) Increasing the relative humidity of the room to 95% D) Requiring all patients to remove their shoes before entering

• Correct Answer: B
• Rationale: Diluting air contaminants through high air-exchange rates and natural cross-ventilation reduces the concentration of infectious droplet nuclei, protecting occupants from tuberculosis exposure.

Q44. During a safety audit of a hotel kitchen, which requirement must be strictly enforced regarding emergency fire exits? A) Emergency exits must be kept locked from the outside at all times for security B) Exits must be clearly marked, illuminated, and kept completely unobstructed at all times C) Exits should be used as temporary storage areas for dry food cartons D) Exit signs should only be written in a foreign language

• Correct Answer: B
• Rationale: Life safety codes require that escape routes remain completely clear and clearly identifiable to facilitate rapid evacuation during a fire emergency.

Q45. What is the minimum recommended ratio of functional latrine seats to the number of male and female students in an Ethiopian school setting, according to national school health standards? A) 1 seat per 200 boys and 1 seat per 200 girls B) 1 seat per 50 boys and 1 seat per 25–30 girls C) 1 seat per 1,000 students regardless of sex D) 1 seat per teacher only

• Correct Answer: B
• Rationale: School sanitation norms dictate higher ratios for girls to accommodate privacy and menstrual hygiene needs, typically targeting 1:50 for boys and 1:25–30 for girls.

Q46. In a correctional facility (prison), severe overcrowding and poor personal hygiene among inmates directly facilitate epidemics of which vector-borne disease transmitted by the human body louse (Pediculus humanus humanus)? A) Yellow fever B) Louse-borne Epidemic Typhus C) Malaria D) Schistosomiasis

• Correct Answer: B
• Rationale: Epidemic typhus, caused by Rickettsia prowazekii, is classic in crowded, unhygienic environments like prisons where body lice proliferate and spread via scratching infected louse feces into broken skin.

Q47. Which administrative control measure is most critical for ensuring safety and hygiene in public market places? A) Forbidding the sale of all fresh agricultural products B) Developing specific market zoning laws that isolate live animal slaughter areas from ready-to-eat food stalls C) Charging flat-rate entrance fees to all individual buyers D) Painting all market stalls with the same bright color

• Correct Answer: B
• Rationale: Zoning prevents cross-contamination between high-risk reservoirs (live animals, offal) and items consumed directly without further cooking.

Q48. What is the primary purpose of color-coding hospital cleaning tools (e.g., mops, buckets)? A) To make the cleaning equipment look visually attractive to patients B) To prevent cross-contamination by separating tools used in high-risk areas (like isolation wards/toilets) from low-risk administrative areas C) To allow cleaning staff to select their favorite colors for shifts D) To reduce the wholesale purchase cost of cleaning detergents

• Correct Answer: B
• Rationale: Restricting specific colored tools to designated areas (e.g., red for toilets, blue for offices) prevents the transfer of pathogens from contaminated zones to sterile environments.

Q49. When evaluating the lighting quality of an institution’s computer laboratory, poor lighting that leads to eye strain, fatigue, and headaches is classified as what type of environmental stressor? A) Biological stressor B) Chemical stressor C) Physical/Ergonomic stressor D) Psychosocial stressor

• Correct Answer: C
• Rationale: Illumination levels directly affect visual comfort and ergonomics; inadequate lighting introduces physical strain on the ocular system.

Q50. Which federal agency or ministry in Ethiopia holds the primary mandate to formulate national environmental health and sanitation guidelines for public and private institutions? A) Ministry of Innovation and Technology B) Ministry of Health (MoH) / Ethiopian Environmental Protection Authority (EPA) C) Ministry of Urban Development and Construction D) Ministry of Finance

• Correct Answer: B
• Rationale: The Ministry of Health, alongside environmental regulatory bodies like the EPA, oversees public health laws, institutional hygiene standards, and environmental sanitation frameworks.