Q.28 A new system of sanitation is needed over the old conservancy system because:
- Athe new system pollutes the city's water supplies
- Bthe system of sanitation has no relation with the city's water supplies
- Cthe old system may pollute the city's water suppliesCorrect
- Dboth the systems of sanitation have an equal chance of polluting water supplies
Solution
Concept
The old conservancy system (manual collection of night soil and refuse) can contaminate water sources, so the water carriage (sewerage) system is preferred.
Step-by-step solution
1. In the conservancy system, night soil and refuse are collected and carried manually, often stored or dumped openly. 2. Leakage and seepage from this waste can reach wells, tanks and other water sources. 3. This creates a health risk through water-borne diseases. 4. The new water carriage system carries waste in closed sewers, which reduces this risk. 5. So the reason is that the old system may pollute water supplies: option C.
Explanation
In the old conservancy system, human waste is handled and dumped in the open. Seepage and runoff from it can pollute the city's water sources. The new water carriage system carries sewage away in closed pipes, so it is safer and more hygienic.
Why the other options are wrong
A: The new system is adopted to reduce pollution, not because it pollutes. B: Sanitation is directly related to the safety of water supplies. D: The two systems do not carry equal risk; the old system is far riskier.
Shortcut
A new system is adopted because the old one has a problem, so pick the option that blames the old system.
Common mistake
Choosing D and thinking both systems carry equal risk, while the closed sewer system is much safer.
Correct answer: C) the old system may pollute the city's water supplies