Mountains are part of which earth sphere

The correct answer will be-lithosphere.

Explanation:

Mountains are the land-forms which rise above the surrounding landforms due to the movement and sliding force of the tectonic plates.  The mountains exhibit a height which is measured in the elevation above the sea level. The mountains possess their own weather conditions and could even lead to the change in the weather conditions.

Since mountains are made up of soil or land, the sphere of the earth involved in the formation of mountain will be known as the lithosphere. The lithosphere is made up of the crust and upper mantle.

Thus, the lithosphere is the correct answer.