JEE Main 18 March 2021 Shift 1 Solved Paper

Troposphere is the lowest layer of all the mentioned layer. Most of the mass like clouds, rains, etc occurs in troposphere. Its height is upto the 10km over the earth surface. Stratosphere is the layer after troposphere. Its height is upto the 70km over the earth surface. Mesosphere is a layer that is situated above the stratosphere and below the thermosphere. The temperature at the top of this layer is very low as compared to the atmosphere found near the earth surface. Its height is upto the 180km over the earth surface.
Thermosphere constitutes the larger part of ionosphere. Its height is upto 270km over the earth surface. Hence, the correct option is (a).