At What Point Is the Vapor Pressure of a Liquid

Multiple Choice

At what point is the vapor pressure of a liquid measured?

A) When molecules escape from the liquid more rapidly than they are recaptured by the liquid.
B) When molecules are recaptured by the liquid more rapidly than they escape from the liquid.
C) When molecules escape and are recaptured at the same rate.
D) When the liquid has been totally converted to vapor.