Why Is the Solar Corona So Much Hotter Than the Photosphere

Multiple Choice

Why is the solar corona so much hotter than the photosphere?

A) Energy is carried upward through the chromosphere by disturbed and tangled magnetic fields.
B) The corona absorbs light from the photosphere very efficiently.
C) The density of the corona is low; following the laws of thermodynamics, the product of density and temperature is a constant.
D) Energy is carried upward through the chromosphere by convective gas motions.