Two Ideal Gases,X and Y,are Thoroughly Mixed and at Thermal

Multiple Choice

Two ideal gases,X and Y,are thoroughly mixed and at thermal equilibrium in a single container.The molecular mass of X is 9 times that of Y.What is the ratio of root-mean-square velocities of the two gases,v_X,rms /v_Y,rms?

A) 9/1
B) 3/1
C) 1/3
D) 1/9