The average kinetic energy ω of molecules = average translational kinetic energy+average translational kinetic energy, which is related to the degree of freedom of molecules. The degree of freedom of monoatomic molecules is only i=3, and that of diatomic molecules is i=5, so the average kinetic energy of helium gas He=3kT/2 is not equal to that of helium gas O2=5KT/2.

So the answer is C.