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.