_________ is regarded as the breath of life.
Nitrogen
Carbon dioxide
Helium
Oxygen
Which one of the following layer is very important for human,plant and animal life?
Troposphere
Stratosphere
Thermosphere
Mesosphere
___________ keeps the Earth's surface warm at night.
Ionosphere
_________ extends up to a height of about 80 kilometres.
The layer lying above the troposphere is called
The first layer is called the
The lower portion of atmosphere contains
Hydrogen
Argon
Which layer is warm near the surface of Earth?
Exosphere
Which is the coldest layer in the atmosphere?
Hydrosphere
________ layer contains electrically-charged ions that help in communication.