Which is the primary process involved in the formation of magma at a rift?

Question

Which is the primary process involved in the formation of magma at a rift?

A Water released by rocks plunging into the asthenosphere lowers melting temperatures.

B Decrease in pressure lowers the melting temperatures of rock materials.

C Plume of heated material rises from deep within the core.

D Friction from moving plates heats rocks until they melt.

Answer 1

Friction from moving plates heats rocks until they melt.

utarch - i concur with what you have said and  apologise for not checking my answer thoroughly

Answer 2

With all due respect to the answer given by Elizabeth H above, the "most" correct answer is C. plume of heated material rising from deep within the core.  I say most correct because option "C" is the closest to being factually correct, although it is not technically correct as stated either.

At rift zones, the earth is spreading apart, like at the mid-Atlantic ridge or the rift valley in East Africa.  The spreading is caused by upwelling convection currents in the upper mantle which split into two different directions as they hit the mantle-crust boundary.  This is not material "rising from deep in the core" but merely currents in the upper mantle.

The reason D is NOT correct is because THAT is the mechanism (partially) responsible for melting plates at areas of subduction (the exact opposite of a rift) where the plates are coming together.