Fill in the blanks:
$(1)$ The substance that spreads pollution is called .......
$(2)$ The full form of $DDT$ is .......
$(3)$ The area from $10 \ km$ to $50 \ km$ above sea level is called .........
$(4)$ Harmful ultraviolet radiation from the sun reaching the earth is blocked by .....

The cause of water pollution is due to

Some statements are given:
$(S_1) \ CO_2$ is a greenhouse gas.
$(S_2)$ Classical smog contains smoke,fog,and a high concentration of $SO_2$.
$(S_3) \ DDT$ is biodegradable.
$(S_4)$ Drinking water should have a high $B.O.D.$
Which is the correct sequence of true $(T)$ or false $(F)$ regarding the above statements?

Write a short note on the effect of Global warming and Greenhouse effect on environment.

Among the following,the one which is not a "green house gas" is:

Ozone is a toxic gas and a strong oxidizing agent. However,it is essential in the stratosphere. Explain what would happen if it were to disappear completely from the stratosphere.