The term 'Biosphere' refers to:

Which substance is now used in refrigerators instead of $CFC$s?

The smog is essentially caused by the presence of

What is the correct sequence of atmospheric layers starting from the Earth's surface?

Pure water would have a $BOD$ value of

Dinitrogen is a robust compound,but reacts at high altitude to form oxides. The oxide of nitrogen that can damage plant leaves and retard photosynthesis is