Three 100-L Flasks at 25°C and 725 Torr Contain the Gases

Three 1.00-L flasks at 25°C and 725 torr contain the gases CH4 (flask A) , CO2 (flask B) , and C2H6 (flask C) .
In which single flask do the molecules have the greatest mass, the greatest average velocity, and the highest kinetic energy?

A) flask A
B) flask B
C) flask C
D) all
E) none