2:25,
=(2×52):(25×52),
=5:1,
故答案为:5:1.
—Hello! Could I speak to Tony?
—________ He is coming. [ ]
A. Hold on, please.
B. This is Tony speaking.
C. Can I take a message?
由两个或两个以上叶轮串联组成的离心泵是()。
A、单级泵
B、多级泵
C、单吸泵
D、双吸泵