Why would you not expect to find metamorphic rocks in the costal plains?

The existing rock must be exposed to high heat, high pressure, or to a hot, mineral-rich fluid. Usually, all three of these circumstances are met. ... If there is too much heat or pressure, the rock will melt and become magma. This will result in the formation of an igneous rock, not a metamorphic rock.

c is the answer to this question. altitude affects the weather because air molecules evaporate.