人工挖孔桩基础时，孔内照明应采用安全矿灯或（）V以下带罩防水、防爆灯具。 ["12","13","14","15"]
美军在科索沃战争中从发现一个机动目标到发动袭击需要（）的时间。 ["1天","10小时","1小时"]
对煤芯的一般要求是可采煤层煤芯采取率不低于（） ["60%","65%","70%","75%"]
You didn't have to write the essay if you didn't want to. It was（） ["compulsory","suitable","alternative","optional"]
在地壳表层分布面积最广的岩石是（） ["火成岩","沉积岩","变质岩","岩浆岩"]
指挥机车的调车指令和用语只能由（）发出。
