A sample of a perfect gas occupies a volume V at a pressure P and obsolete temperature T. The mass of each molecule is m, which of the following expressions given the number of molecules in the sample?

• A

  $\frac{\mathrm{PV}}{\mathrm{m}}$

• B

  $\frac{\mathrm{k}}{\mathrm{PVT}}$

• C

  $\frac{\mathrm{m}}{\mathrm{k}}$

• D

  $\frac{\mathrm{PV}}{\mathrm{kT}}$