Answer:
A. all the atoms have the same average speed
Explanation:
The entropy of the two monatomic gases (helium and neon) depends on temperature of the sealed container. Increase in temperature of the container increases the speed of the atoms while decrease in temperature of the container decreases the speed of the atoms. Also at constant temperature, all the gaseous atoms will move at a constant speed (that is randomly or no direction).
Since, the sealed container was brought into thermal equilibrium, meaning that the temperature of the system is constant. Thus, all the atoms have the same average speed.