Choose the correct option.

1. Radio waves transmitted from the Earth are reflected back to the Earth in ______________.
   1. troposphere
   2. stratosphere
   3. mesosphere
   4. thermosphere
2. The ozone layer is a part of
   1. stratosphere
   2. troposphere
   3. thermosphere
   4. mesosphere
3. The troposphere has the largest concentration of
   1. oxygen
   2. nitrogen
   3. water vapour
   4. atom
4. _____________ a trillion-ton iceberg has broken off from Antarctica's Larsen C ice shelf.
   1. A-68
   2. A-69
   3. A-70
   4. A-67
5. Melting of the glaciers would result in the rise in _____________.
   1. sea levels
   2. temperature 
   3. carbon dioxide
   4. humidity

Fill in the blanks.

1. Layer of gases which envelops the Earth is called _________________.
2. Air contains a variable amount of ________________ about 1 to 4 per cent.
3. The upper limit of mesosphere is called the ________________.
4. The layer of atmosphere where airplanes fly is called ________________.
5. Meteors burn on entering the atmosphere in the presence of ______________.

Write (T) for true and (F) for false.

1. The atmosphere makes life possible on Earth.
2. Troposphere has high night-shinning (noctilucent) clouds.
3. Temperature increases with altitude in the troposphere.
4. The air resting over the poles is dense and heavy.
5. Jet planes move in the mesosphere.

Differentiate between Oxygen and Carbon dioxide.

Differentiate between Ozone layer and Atmosphere.