矿山安全技术 管线组焊、修口或封焊隔离球孔前，应先作可燃气体浓度检测试验，当可燃气体的浓度达到爆炸下限的( )以下时，方可进行动火作业。
A. 10%
B. 25%
C. 30%
D. 50%
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矿山安全技术 露天开采是用一定的开采工艺，按一定的开采顺序，剥离岩石、采出矿石的方法。其中，( )开采工艺劳动效率高，易实现生产过程自动化，但只能用于松软矿岩。
A. 间断式
B. 连续式
C. 半连续式
D. 分步式
Questions 11 to 18 are based on the conversation you have just heard.
A. She will constantly inform him of the date.
B. She will gladly do the missed jobs for him.
C. She will be able to inform him of what he missed.
D. She doesn’t think they have been doing that much to be concerned.
对数据操作时会引起的异常包括修改异常、______异常和删除异常。
What do we know from the talk
A. Because she’s writing a book.
Because she’s learning how to drive a car.
C. Because she’s making toys.
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