Why Is It More Difficult to Lose Excess Body Heat

Why is it more difficult to lose excess body heat on a hot day?

A) Because you gain heat from the outside
B) Because as air temperature gets closer to body temperature, heat loss from the body to the air by evaporation slows
C) Because as air temperature gets closer to body temperature, heat transfer from the warmer body to the cooler air by convection slows
D) Because very hot air causes heat stroke, where the body's mechanisms for losing heat shut down
E) Because blood circulation nearing the skin gets warmer rather than getting cooler