离心泵启动时，应做到（）。
A.吸水管闸阀关闭
B.压水管闸阀关闭
C.排气阀应关闭
D.压力表应关闭
参考答案：B, C
—How was the 2008 Beijing Olympic opening ceremony?
—________ that the whole world was attracted.
A．It was very fantastic
B．Such fantastic was it
C．So fantastic was it
D．So fantastic it was
包括传播行为、传播活动在内的传播现象，是一种（）
A.心理现象
B.生理现象
C.自然现象
D.社会现象
