On Earth (And in the Past,on Mars),volcanoes Have Been Vital

Multiple Choice

On Earth (and in the past,on Mars) ,volcanoes have been vital for keeping the planet warm.This is because

A) heat conducted from the molten mantle to the surface near volcanoes,where the crust is thin,is a major heat source for the atmosphere.
B) heat released along the major rift zones is the biggest source of heating for the atmosphere.
C) direct heat input by underwater volcanoes keeps the oceans from freezing.
D) they have replenished the CO₂ (a greenhouse gas) that is washed out of the atmosphere by rain.