The picture below shows metamorphic rocks on the earth's surface.

Referring to the attached image below which represents the complete rock cycle, we will find that:
The metamorphic rocks are formed due to heat and pressure applied either on igneous rocks or on sedimentary rocks.
This means that heat and pressure are the main factors in the formation of metamorphic rocks.

Based on the above, the best choice would be:
a. extreme changes in temperature and pressure

Sound waves actually travel much faster in water than air, but words and the direction of the noise are distorted.