Equal Masses of Hydrogen and Helium Gas Are at the Same

Equal masses of hydrogen and helium gas are at the same temperature in vessels of equal volume. The atomic mass of helium is four times that of hydrogen. If the total mass of both gases is the same, the ratio of the pressure of helium (He) to that of hydrogen (H2) is

A) .
B) .
C) 1.
D) 2.
E) 4.