單項(xiàng)選擇題

In the International Code of signals，a group of three letters indicates（）.

A.urgency or an emergency
B.the vessel's national identity signal
C.a group from the general signal code
D.a group from the medical signal code

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單項(xiàng)選擇題

In order to prevent galvanic corrosion，an aluminum boat must be insulated from the davits and gripes. Which of the following is acceptable as an insulator?（）

A.Hard rubber
B.Canvas
C.Leather
D.Sponge rubber

單項(xiàng)選擇題

In battery charging rooms，ventilation should be provided（）.

A.at the lowest point
B.near the batteries
C.at the highest point
D.only when charging is in progress