A.0.5m B.0.6m C.0.7m D.0.8m
A.8% B.10% C.15% D.18%
A.后退向下,自重切土 B.直上直下,白重切土 C.前進(jìn)向上,強(qiáng)制切土 D.后退向下,強(qiáng)制切土