If P is the pressure, V the volume, R the gas constant, k the Boltzmann constant and T the absolute temperature, then the number of molecules in the given mass of the gas is given by 

• A

  $\frac{\mathrm{PV}}{\mathrm{RT}}$

• B

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

• C

  $\frac{\mathrm{PR}}{\mathrm{T}}$

• D

  PV