Correct option (A) 1: 1
Explanation:
Average kinetic energy per molecule per degree of freedom = 1/2 kT. Since,both the gases are diatomic and at same temperature (300 K), both will have the same number of rotational degree of freedom i.e., two. Therefore, both the gases will have the same average rotational kinetic energy per molecule
Thus, ratio will be 1: 1.