$...............$ is any undesirable change in the physical,chemical,or biological characteristics of air,land,water,or soil.

$DDT$ is a

Why is $CNG$ considered a better fuel than diesel?
$(a)$ It cannot be adulterated.
$(b)$ It takes less time to fill the fuel tank.
$(c)$ It burns more efficiently.
$(d)$ It is cheaper.
$(e)$ It is less inflammable.
Choose the most appropriate answer from the options given below:

The measurement of the amount of organic matter in water is known as:

Which of the following metals is a water pollutant and causes sterility in human beings?

$SO_{2}$ pollution affects