Show That SE = hr! (!_cond 얕 mc²

Answer(a)   the matererials that are in contact, the two materials and the nature of their surfaces/// (b)/// the force pushing the two surfaces together, pushing the surfaces together causes the more of the asperities to come together and increases the surface area in contact with each other

The answer is d, you can easily test a theory! hope i you : )

C. it comes from the core of the earth.