An ideal monatomic gas initially at temperature T0 and volume V0 undergoes one of the four reversible processes listed below. Which process results in the greatest positive entropy change of the gas?
I. Heated at constant volume from T0 to 2T0.
II. Heated at constant pressure from T0 to 2T0.
III. Isothermal expansion from V0 to 2V0.
IV. Isothermal compression from V0 to 2V0.
a) Process I
b) Process IV
c) Process II
d) Process III