Choose the best answer. magma forms at mid-ocean ridges because:
a volatiles (sea water) is added to hot mantle rocks, lowering their melting temperature.
b heat is generated by friction along normal faults caused by extension of lithosphere.
c the lithosphere is thinned at divergent boundaries, allowing hot mantle rocks to melt due to decompression.
d the earth is hotter at divergent boundaries.

The best answer for the given question out of the four options provided is

option C.

Explanation:

Decompression melting also known as adiabatic melting of the mantle is most commonly linked with divergent boundaries of the plate, which serves as the point of the 2 tectonic plates  from one another along a mid ocean ridges leading to  the generation of magma.  

Therefore, thinning of Lithosphere at diverging boundaries , allows hot mantle rocks to melt as a result of decompression.