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①元谋人遗址②北京人遗址③山顶洞人遗址④半坡遗址 [ ]

A．①②

B．②③

C．②④

D．③④

The most variable factor in the control of broken stowage is（）.

A.the use of excessive amounts of dunnage

B.the use of excessive amount of filler cargo

C.the failure to stow some item in neat and uniform rows and tiers

D.the skill, industry and interest of the longshoremen