A. 一般 B. 可以 C. 應(yīng)當(dāng) D. 必須
A.8% B.9% C.10% D.12%
A.一次開(kāi)挖 B.分段開(kāi)挖 C.分層開(kāi)挖 D.有序開(kāi)挖