Energy is
a. the same as mass.
b. the capacity to do work.
c. being constantly used up.
d. all of the above

B. The capacity to do work.  

Explanation:

That's the definition of energy.

A. is wrong. Energy is different from mass. However, according to Einstein's famous equation, energy can be converted into mass and vice versa.

C. is wrong. According to the Law of Conservation of Energy, it can be converted from one form to another, but it cannot be destroyed or created.

it is a learned trait

explanation:

"a.) well–developed vascular system."