The Difference in the Molar Heat Capacity at Constant P

Multiple Choice

The difference in the molar heat capacity at constant P and constant V is (assume ideal gas) .

A) equal to R for monotomic gas.
B) equal to 2R for diatomic gas.
C) equal to NR for polyatomic gas,where N is the number of atoms in a polyatomic molecules.
D) equal to R for all gases.
E) (A) and (D)