【单选题】
Centrifugal pumps, however, can be designed with a number of impellers （） to attain a large amount of liquid.
A、in series
B、in parallel
C、assembled
D、together
查看正确答案
A、centrifugal pump is cheaper than reciprocating pump B、the size of centrifugal pump with same capacity is smaller than that of reciprocating pump C、centrifugal pump makes maintenance easier than reciprocating pump does D、all of the above
