造成吊钩吊物摇摆主要原因是（）。
A.吊钩变形
B.现场环境复杂
C.吊物重心偏移
参考答案：C
Which topic is NOT required to be discussed at the pre-transfer conference?（）
A.Identity of the product to be transferred
B.Details of transferring and receiving systems
C.Emergency shutdown procedures
D.Estimated time of finishing cargo
丹参醌类成分属于（）
A.苯醌
B.萘醌
C.菲醌
D.羟基蒽醌
E.蒽酚或蒽酮
