As a Comet Enters the Inner Solar System, Its Coma

As a comet enters the inner Solar System, its coma can grow to a large size, as large as some planets in a few cases.What causes this growth?

A) Tidal forces from the inner planets pull material off the comet.
B) The comet moves at a higher velocity near perihelion and loose material is dislodged.
C) The comet's tectonic action is triggered by the Sun's strong gravity.
D) The rotation (spin) of the comet increases near perihelion due to angular momentum conservation.
E) The Sun's radiation heats the comet, allowing materials to sublimate into a cloud.