Despite the Planet's Close Proximity to the Sun,water Ice Remains

Multiple Choice

Despite the planet's close proximity to the Sun,water ice remains on the surface of Mercury because it

A) is permanently shielded from the Sun by crater walls at the north and south poles.
B) exists as permafrost below the thermally insulating surface,being exposed only by occasional impacts.
C) is continuously replenished by fresh impacts from comets.
D) is continuously replenished by condensation of water vapor from volcanoes.