Why Is So Much Mafic Magma Erupted Along Mid-Ocean Ridges

Multiple Choice

Why is so much mafic magma erupted along mid-ocean ridges?

A) Basaltic mantle under the ridge is hot enough to completely melt if seawater is added.
B) Lowered pressures decrease the temperatures at which mafic magma can partially melt from massive, extensive, rising plumes of mantle peridotite.
C) The subducting, oceanic slab sinks so deep that eventually it melts, producing massive quantities of mafic magma.
D) The mantle beneath the ridges is enriched in thorium, uranium, and potassium, causing strong heating due to energy from radioactive decay.