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單項選擇題

The vapors given off by heated fuel oil are heavier than air and are（）.

A.odorless
B.explosive
C.nontoxic
D.visible

單項選擇題

If it becomes necessary to pump bilges while a vessel is in port, which of the following procedures should be followed?（）

A.Pump only if the discharge is led to a shore tank or barge
B.Pump only during the hours of darkness
C.Pump only on the outgoing tide
D.Pump only as much as is necessary