The Noble Gases, Listed by Increasing Molecular Weight, Are He

The noble gases, listed by increasing molecular weight, are He, Ne, Ar, Kr, Xe, and Rn. If samples of 1 mole each of these gases are placed in separate containers and heated to 300 K, which gas has the greatest internal energy and the molecules of which gas have the lowest average speed?

A) The He has the greatest internal energy, and Rn has the lowest speed.
B) The Rn has the greatest internal energy, and He has the lowest speed.
C) All the gases have the same internal energy, and Rn has the lowest speed.
D) All the gases have the same internal energy, and He has the lowest speed.