21. An ideal gas may be taken from one state to another state with a different pressure, volume, and temperature along several different paths. Quantities that will always be the same for this process, regardless of which path is taken, include which of the following?
I. The change in internal energy of the gas
II. The heat exchanged between the gas and its surroundings
III. The work done by the gas
(A) I only
(B) II only
(C) I and III only
(D) II and III only
(A) I only
(B) II only
(C) I and III only
(D) II and III only