單項(xiàng)選擇題

If the hatch cover does not move, （）should be checked.

A. the open valve
B. the stop valve
C. the steam valve
D. the close valve

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單項(xiàng)選擇題

To ensure the safety in operating hatch covers, oil the moving parts （）.

A. monthly
B. every three months
C. once monthly
D. every two months

單項(xiàng)選擇題

During operation, the （）should check the working condition of the derrick.

A.foreman
B.operator
C.opener
D.stevedore