They have __________ the film before.[ ]
A. see
B. to see
C. seeing
D. seen
答案:D
A.强
B.多
C.大
D.重
被吊物件大于天车额定负荷()时,不允许三个机构同时开动。
A、5%
B、10%
C、15%
D、50%