矿井探水
参考答案：
采掘前，用超前钻孔来探明采掘工作面周围的水源和含水情况的作业
Last week, only two people came to look at the house, __________ wanted to buy it.
A．none of them
B．both of them
C．none of whom
D．neither of whom
手术后心肌梗死一般发生在术后（）
A.<1周
B.2周
C.3周
D.4周
E.5周
