If three unreactive gases having partial pressures $P_A$,$P_B$,and $P_C$ and their moles are $1$,$2$,and $3$ respectively,then their total pressure will be:

• A
  $P = P_A + P_B + P_C$
• B
  $P = \frac{P_A + P_B + P_C}{6}$
• C
  $P = \frac{\sqrt{P_A + P_B + P_C}}{3}$
• D
  None