As temperature changes, rocks expand and contract. The rocks eventually break into
smaller pieces. Which process accounts for
this expansion and contraction of rocks?

Thermal heating and cooling

Explanation:

This process described results from thermal heating and cooling as a mechanism of mechanical weathering of rock bodies.

It is often more pronounced in the arid regions of the world where there is a significant difference between day and night temperatures. With mechanical weathering, rocks are broken down into fragments by physical disintegration. During the day, the high temperature causes the rock to expand significantly. At night, the rock contracts and on the long run, joints and fractures begins to appear on the rock surface.

C) electrons encircling a nucleus with neutrons and protons