单项选择题
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
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?（）
单项选择题 In battery charging rooms，ventilation should be provided（）.
单项选择题 If passengers are on board when an abandon ship drill is carried out，they should（）.