When rocks are exposed to heat, they which can contribute to thermal stress.

Expands

Explanation:

Rocks being exposed to heat tends to expand. This expansion creates thermal stress in the area surrounding that rock. When this expansion takes place under the earth's surface, this expansion makes the tectonic plates to move which further becomes the cause of earthquakes. Hence, the answer is 'expands'.

the second type of galaxy is called a barred spiral, which has a thing called a bar straddling the nucleus

the answer is d.) homologous; have mammary glands