The density of hydrant is approximately 9x10^-5 g/cm^3 well the density of helium is approximately 2x10^-4 g/cm^3 which of the following is true
A: the density of helium is approximately two times the density of hydrogen
B: the density of helium is approximately 20 times the density of hydrogen
C: density of hydrogen is approximately 20 times the density of helium
D: the density of hydrogen is approximately two times density of helium