单项选择题

A.开槽支撑、边挖边撑、分层开挖,严禁超挖
B.开槽支撑、先撑后挖、分层开挖,严禁超挖
C.支撑开槽、先撑后挖、分层开挖,严禁超挖
D.支撑开槽、边挖边撑、分层开挖,严禁超挖