一切电话中断后，连续发出同一方向的列车时，两列车的间隔时间应按区间规定的运行时间另加5min。
参考答案：错
30. Had it not been for the fact that I _____ absent, I would have asked you to do this right now.
A．had been
B．were
C．should be
D．Was
制取较纯的一氯乙烷，用下列哪种方法最好
A．乙烷和氯气取代
B．乙烯加成氢气，再用氯气取代
C．乙烯和氯化氢加成
D．乙烯和氯气加成
