单项选择题
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
In battery charging rooms，ventilation should be provide...
单项选择题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
