At ordinary temperatures, the molecules of an ideal gas have only translational and rotational kinetic energies. At high temperatures they may also have vibrational energy.
As a result of this, at higher temperature
A. `C_(v)=(3)/(2)R` for a monoatomic gas
B. `C_(v)gt(3)/(2)R` for a monoatomic gas
C. `C_(v)lt(3)/(2)R` for a diatomic gas
D. `C_(v)=(5)/(2)R` for a diatomic gas