螺杆泵的备用泵启动时应按（）操作。
A.停泵操作规程
B.启泵操作规程
C.盘车操作规程
D.切换操作规程
参考答案：B
—Did you forget about my birthday?
—____________ I’ve booked a table at Michael’s restaurant for this evening.
A．So what?
B．I’m afraid so.
C．How could I?
D．For sure.
—Did you hear about the air crash? I feel so lucky!
—Yes．If you _____ that flight, I _____ speaking to you now．
A．were taking; wouldn't be
B．took; wouldn't have been
C．had taken; wouldn't be
D．had taken; wouldn't have been
