炮洞直径为0.2~0.5m,洞穴成水平或略有倾斜,深度小于5m,用集中药于炮洞中进行爆炸的方法称为()。
A. 钢钎炮
B. 猫洞炮
C. 药壶炮
D. 深孔爆破
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The magnetic compass magnets are acted on by the horizontal component of the Earth’s total magnetic force. This magnetic force is GREATEST at the().
A. north magnetic pole
B. south magnetic pole
C. magnetic prime vertical meridian
D. magnetic equator