Answer:
A. Three types of changes that occur in the process of metamorphism are: 1. Pressure: When rocks are subjected to high pressure, they can change form without melting. This is called pressure metamorphism. 2. Temperature: If rocks are heated to high temperatures, they can change form without melting. This is called thermal metamorphism. 3. Chemical changes: Rocks can undergo chemical changes due to the introduction of fluids. This is called hydrothermal metamorphism. B. During pressure metamorphism, the rock structure changes due to the pressure, causing minerals to reorient themselves and form new minerals. During thermal metamorphism, the rock structure changes due to the heat, causing minerals to recrystallize and form new minerals. During hydrothermal metamorphism, the rock structure changes due to the introduction of fluids, which can cause new minerals to form and old minerals to dissolve.