单项选择题
A.of B.to C.on D.with
Keep clear（）the buoy.A.toB.onC.ofD.for
单项选择题Keep clear（）the buoy.
A.to B.on C.of D.for
In the International Code of signals，a group of three l...
单项选择题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
In order to prevent galvanic corrosion，an aluminum boat...
单项选择题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
