Jet aircrafts fly in the :

How long should water be boiled to kill germs?

Which gas present in the atmosphere helps plants to prepare their food?

What do we need to breathe?

The layer of the atmosphere in which we live is the :

Air is a mixture of many:

Which is needed by human body to carry out life processes?

Which chemical is added to water to kill germs?

The atmosphere is divided into:

Removing impurities by passing water through a thin cloth or filter paper is called: