Athletes Are Reminded to Drink More Water When They Are

Athletes are reminded to drink more water when they are exercising in cold weather because it is easy to get dehydrated. The main reason for this is

A) the increased dew point at lower temperatures.
B) the higher vapour pressure of water at lower temperatures.
C) the lower relative humidity of the air at lower temperatures.
D) higher relative humidity.
E) lower vapour pressure.