How does the magma chamber work?

A. The magma chamber collects the magma deep underground. When the core moves, the magma chamber erupts.

B. The magma chamber holds the lava until something aggravates it. It then releases a gas, followed by an eruption.

C. The magma chamber collects the magma deep underground. It naturally pushes upward, and when pressure is high enough, it can split from the main vent.

D. none of these