answer:Collisions between gas particlCollisions between gas particles or collisions with the vessel walls are perfectly elastic.
explanation:As long as an ideal gas is maintained at a constant temperature, the average kinetic energy of the molecules is said to be constant. In fact, what we call the temperature of a body at the macroscopic scale is just a representation of the kinetic energy carried by its atoms or molecules as they vibrate inside the body.
Now, if the kinetic energy of this oxygen gas is constant, it is because the collisions between the particles are assumed to be perfectly elastic. No energy is lost during the collisions. The rationale behind this assumption is that the particles are very tiny.
The answer which corresponds best to the explanation above is b. Collisions between gas particles are elastic; there is no net gain or loss of kinetic energy.