The ice on the front windshield of the car had formed when moisture condensed during the night.The ice melted quickly after the car was warmed up the next morning because the defrosting vent,which blows on the front windshield,was turned on full force.
Which if the following, if true, most seriously jeopardizes the validity of the explanation for the speed with which the ice melted?
A, The side window with no ice condensation on them.
B, Even though no attempt was made to defrost the back window, the ice there melted at the same rate as did the ice on the front shield.
C, The speed at which the ice on the window melts increases as the temperature of the air blown on the window increases.
D, The warm air from the defrosting vent for the front windshield cools rapidly as it dissipates throughout the rest of the car.
E, The defrosting vent operates efficiently even when the heater,which blows the warm air toward the feet or faces of the driver and passengers,is on.

The key is B.
D为什么不对呢？如果空气变冷了不也影响除霜的速度吗？
请大家指点指点。