A.逐層開(kāi)挖,先撐后挖B.逐層開(kāi)挖,先挖后撐C.分層開(kāi)挖,先挖后撐D.分層開(kāi)挖,先撐后挖
A.前進(jìn)向上,強(qiáng)制切土B.前進(jìn)向先,強(qiáng)制切土C.后退向上,強(qiáng)制切土D.后退向下,強(qiáng)制切土
A.人工開(kāi)挖B.機(jī)械開(kāi)挖C.爆破開(kāi)挖D.推土機(jī)開(kāi)挖