單項選擇題

A towboat is pushing barges ahead at a dangerously fast speed when（）.

A.the towboat vibrates when backing down
B.the roostertail exceeds the height of the main deck
C.a strain is placed on the face wires
D.water comes over the foredeck of the lead barges

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單項選擇題

A tow of 9 barges is made up three abreast and three long. The towboat is faced up to the center string which is known as the（）.

A.main string
B.push string
C.power string
D.face string

單項選擇題

A spreader bar is used to（）.

A.increase the lifting capacity
B.increase the lifting radius
C.protect the slings
D.protect the upper part of a load