If the atmospheric pressure is $P_a$,then the pressure $P$ at depth $h$ below the surface of a liquid of density $\rho$ open to the atmosphere is:

• A
  $P_a - \frac{\rho gh}{2}$
• B
  $P_a - \rho gh$
• C
  $P_a$
• D
  $P_a + \rho gh$