Which of the following best describes the thermosphere?
question 15 options:

a-heavier gases such as hydrogen and helium stay at the bottom of the thermosphere.

b-the thermosphere sits directly below the troposphere.

c-the atmosphere is so thin that gas molecules rarely contact each other.

d-lighter gases such as nitrogen and oxygen rise to the top of the thermosphere.

C- The atmosphere is so thin that gas molecules rarely contact each other

Explanation:

The theromosphere is one of the several atmospheric layers of Earth. This layer the top one, thus it is the layer that sits on top of the other layers, and it also contact with the exosphere which is a transitional zone between Earth's atmosphere and space.

The name of this layer comes from the high temperature in it, reaching up to 1,000 C degrees. The temperature gradually rises with elevation.

This atmospheric layer is hot because the gases like nitrogen and oxygen absorb the solar radiation and then release thermal radiation. Weirdly enough, despite the very high temperatures, it actually doesn't feel hot at all in the thermosphere. The reason for that is that the atmosphere is very thin, the molecules of the gasses very sparsely distributed, so they don't collide with each other, so the heat can not be transferred.

a is the answer i believe.