The Reason the Temperature on the Dark Side of Mercury

Multiple Choice

The reason the temperature on the dark side of Mercury is warmer than originally expected is that:

A) Mercury's large iron core conducts heat through the planet.
B) Mercury does not rotate synchronously with its orbital period.
C) several very active volcanoes on Mercury, produced by tidal stresses from the Sun, produce excess heat.
D) winds in Mercury's tenuous atmosphere carry heat from the daytime side to the night side.