$A$ gas is filled in a vessel at a pressure given by $P = (6.02 \times 10^{23})kT$,where $k$ is the Boltzmann constant and $T$ is the absolute temperature. The number of molecules per unit volume of the gas is:

• A
  $6.02 \times 10^{23}$
• B
  $1$
• C
  $\frac{6.02 \times 10^{23}}{8.31}$
• D
  $6.02 \times 8.31 \times 10^{23}$