爆炸工和爆炸点之间的距离一般取决于药量、下药深度、地形、地表

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问题单项选择题

爆炸工和爆炸点之间的距离一般取决于药量、下药深度、地形、地表、土壤结构和来自附近树木和树枝的空中隐患。最低安全距离为（）米。

A、20米

B、25米

C、30米

D、50米

答案

参考答案：C

选择题

— How is your mother doing? Is she _____?

— Oh, thank you. As a matter of fact, she _____. [ ]

A. looking up; has recovered

B. picking up; is already back on her feet

C. lifting up; is well again

D. taking up; has already been back on her feet

填空题

光电检测技术研究的主要内容是（）、电信号处理技术。