—Putting on a happy face not only helps us make friends but also makes us feel better.

—__________.

A．I’d love to

B．I’m with you on that

C．It’s up to you

D．It’s my pleasure

往复泵的严重缺点是（）。

A.不易操作

B.能耗大

C.压力低

D.流量不均匀