`C_p` is always greater than `C_v` for a gas, which of the following statements provide, partly or wholly, the reason for this?
(i) No work is done by a gas at constant volume
(ii) When a gas absorbs heat at constant pressure, its volume must change
(iii) For the same change in temperature, the internal energy of a gas changes by a smaller amount at constant volume that at constant pressure
(iv) The internal energy of an ideal gas is a function only of its temperature

Options

A. No work is done by a gas at constant volume.
B. When a gas absorbs heat at constant pressure, its volume must change
C. For the same change in temperature, the internal energy of a gas changes by a smaller amount at constant volume than at constant pressure.
D. The internal energy of an ideal gas is a function only of its temperature.