At mid-ocean ridges, as two plates diverge:

A) solid mantle in the asthenosphere rises toward the surface and begins to melt due to decompression
B) solid mantle in the asthenosphere rises toward the surface and begins to melt due to the addition of heat
C) liquid mantle in the asthenosphere rises toward the surface

Mid-Ocean Ridges

Underwater mountain ranges formed by plate tectonics, where new oceanic crust is created by volcanic activity along divergent plate boundaries.

Asthenosphere

The highly viscous, mechanically weak, and ductilely deforming region of the upper mantle of the Earth.

Decompression

The process of reducing pressure in a physical system, often leading to the release of dissolved gases or the formation of bubbles in a liquid.