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單項(xiàng)選擇題

Before welding can be done in a tank that has carried petroleum products, a certificate must be obtained from（）.

A.the customs
B.the register bureau of shipping
C.the shipyard fire department
D.a certified gas chemist

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Between the side frames on a vessel, support for the deck beams is provided by（）.

A.stanchion
B.brackets
C.web frames
D.deck stringers

單項(xiàng)選擇題

Bilge keels are fitted on ship to（）.

A.assist in drydock alignment
B.improve the vessel's stability
C.protect the vessel from slamming against piers
D.reduce the rolling of the vessel

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