Answer: A. The vertical temperature line indicates no change in temperature at those altitudes.
Explanation: In the troposphere, as we move upwards in altitude the temperature falls 1°C for every 66 km. But near the stratosphere in the tropopause region, the temperature becomes constant because this part does not significantly absorb solar radiation. Most of the heat gets trapped into the ozone layer that is situated above in the stratosphere and then the rest of the heat is radiated to the lower layers of the atmosphere.