问题
选择题
Email,as well as telephones ________ an important part in daily communication.[ ]
A. is playing
B. have played
C. are playing
D. play
答案
答案：A
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Email,as well as telephones ________ an important part in daily communication.[ ]
A. is playing
B. have played
C. are playing
D. play
答案：A
分为四组，任选一组作答。每组10个单项选择题。每题的备选项中，只有1个最符合题意。
(一) 矿山安全技术 |
天然气储罐检修动火时，应经放空、吹扫、消洗、强制通风、取样分析，可燃气体浓度小于或等于其爆炸下限的（）为合格。
A．15%
B．20%
C．25%
D．30%