Why Are Fats a Better Source of Energy Than Carbohydrates

Multiple Choice

Why are fats a better source of energy than carbohydrates on a per carbon basis?  

A) Fats are comprised of other atoms besides carbon and oxygen that increase its ATP yield.
B) Fats have more hydrogenbound in its fatty acid chains, which allows them to react more with oxygen.
C) Fats do not completely break down, and the by-products increase ATP yield.
D) Fats require fewer reactions with oxygen to completely break down, thus increasing its ATP yield.
E) Fats require more reactions with oxygen to completely break down.