Concept:Proper sewage disposal breaks the cycle of disease transmission by keeping human waste out of reach of flies.
Explanation:Water closets and septic tanks are fully enclosed waste disposal systems.
They carry contaminated faeces safely away from the living environment.
Because the system is enclosed, flies cannot come into contact with the faeces.
Bucket and pit latrines often leave faeces exposed or only partially covered.
Flies can easily land on such exposed faeces and pick up disease-causing germs.
These flies then spread the germs to food and water, causing infections.
Water closets and septic tanks prevent this by completely isolating faeces from flies.
Thus, they are preferred because they safely contain contaminated material and stop flies from spreading diseases.
The reason is not mainly about cost, chlorine in the flushing water, or merely reducing fly breeding.
The key advantage is that contaminated faeces are completely kept away from flies.
Answer:B. contaminated faeces are completely kept away from flies