Which of the Following Statements Regarding the Mixing of Gases

Which of the following statements regarding the mixing of gases is correct?

A) More massive gases settle to the bottom of a container, leaving lighter gases near the top.
B) The relative proportions of gases in a mixture vary throughout the container, depending on the pressure.
C) Nonpolar gases do not mix with polar gases.
D) All gas mixtures are homogeneous.
E) Gases mix more uniformly at lower temperatures.