Total earth's surface covered by water is: (in $\%$)

Name the various organisms involved in the nitrogen cycle.

What would happen if all the oxygen present in the environment were converted to ozone?

Give two examples where oxygen is not playing any role in supporting life.

State whether the following statement is True or False:
The heating of the air causes the water vapour in the air to condense in the form of tiny droplets.

List three human activities responsible for the pollution of water bodies.