What causes stars to form out of such gas clouds? A. gravity B. heat from starlight C. chemical transformations D. evaporation

Gravity causes stars to form out of gas clouds.

Explanation:

The formation occurs in molecular clouds in the interstellar space. The atoms of light are first forced under sufficient pressure so that their nuclei undergo fusion. The gravitational force is responsible for this fusion to begin.

The gases present in these clouds clump to form molecules with higher densities. Due to the internal gravitational disturbance, there begins to occur a collapse of the denser regions of the cloud. As the collapse continues to occur, the temperatures begin to increase and each of the smaller clouds will eventually form a star.