在离心泵的运行中，压力、流量应平稳，压力波动应不大于（）。
A、2%
B、5%
C、8%
D、10%
参考答案：B
— Would you like ______ with me this Sunday?
— Sorry, I have something ______. [ ]
A. going shopping; to do
B. to go shopping; to do
C. going shopping; doing
D. to go shopping; doing
和
两种离子的电子层结构相同，则a等于