The Very Rapid Recession of the Edge of the White

The very rapid recession of the edge of the white polar cap region toward the poles in springtime on Mars is caused by the:

A) increased growth of vegetation from mid-latitudes toward the poles.
B) evaporation of a thin layer of water ice crystals (frost or snow) .
C) melting of a thick layer of solid water ice and the subsequent run-off of water.
D) rapid evaporation of carbon dioxide ice.