Suppose You Are Outside in Very Cold Temperatures,wearing a Winter

Suppose you are outside in very cold temperatures,wearing a winter coat that is quite effective at keeping you warm.Which of the following is true?

A) The coat is the source of the heat that keeps you warm.
B) Your body generates the heat that keeps you warm.
C) The coat prevents your body's heat from escaping to the surrounding air.
D) a and c
E) b and c