A.90° B.100° C.110° D.120°
A.45° B.大于45° C.75° D.小于60°
A.人員不準站在吊桿底下 B.作業(yè)人員應(yīng)足夠 C.操作應(yīng)盡量快,以策安全 D.雙桿必須互相配合好