Heat can be transferred through conduction, convection, and radiation. What is necessary in order for heat to be transferred by conduction? A.
Heat must be transferred through space.
B.
Heat must be transferred in the form of currents.
C.
The substances must be liquids or gases.
D.
The objects must be in direct contact with one another.

it would be C

sorry if I am wrong I tryed to think, At least I try!

answer: the metamorphic rocks are formed when they are exposed to high pressure and high temperatures. this happens when one of the earth's plates comes in contact with the other plate by traveling in opposite directions, straight into each other or slipping under one another. the friction that is caused by this activity results in   melting of rocks and when it cools they are known as metamorphic rocks. this process needs a controlled amount of pressure and temperature otherwise it may turn into magma.