Need help on the question below...I know it is not C or D

Question

The formation of metamorphic rocks depends on all of the following except
a. the composition of parent rocks
b. Earth's magnetic field
c. temperature
d. pressure
Thanks

Answer 1

Pressure is he best answer.

Answer 2

I disagree with your answer although I'm certainly no expert on rocks/geology processes, etc. Pressure is a very real part of metamorphic rock formation.
See http://en.wikipedia.org/wiki/Metamorphic_rock

I can remove your answer if you wish.