The $BOD$ limit prescribed by the Central Pollution Control Board $(CPCB)$ for the discharge of industrial and municipal wastewater into natural surface water bodies is .....

Why is $CNG$ considered a better fuel than diesel/petrol?
$I.$ $CNG$ burns most efficiently without leaving any unburnt remnant behind.
$II.$ $CNG$ is cheaper than petrol or diesel.
$III.$ $CNG$ cannot be siphoned off by thieves and adulterated like petrol or diesel.
Which of the statements given above are correct?

Brewery and sugar factory waste alters the quality of a water body by increasing

The natural aging of a lake by nutrient enrichment of its water is known as $..........$

$CNG$ is considered a more efficient fuel. Which of the following statements is incorrect regarding it?

It is a common practice to undertake desilting of the overhead water tanks. What is the possible source of silt that gets deposited in the water tanks?