Which of the following statements represents the advantage of rotary pumps as compared to reciprocating pumps?（）

A. The high discharge pressure of the rotary pumps permits a larger volume of fluid per unit time than the reciprocating pump
B. Rotary pumps are capable of pumping more fluid than reciprocating pumps of the same weight
C. Rotary pumps occupy only one-half the space of reciprocating pumps
D. Rotary pumps eliminate discharge slippage of the pumped liquid, while this does not hold true for a reciprocating pum