单项选择题
A.unscrewing the bulb during the daylight
B.switching the light on only when necessary
C.taking no action as there is no way on saving power
D.taking no action as they shut off automatically in daylight
单项选择题 In（）convention，a vessel which carries more than 12 passengers shall be deemed as a passenger ship.
单项选择题 How many operators are needed／required on board according to the provisions of the International Convention for the Safety of Life at Sea，1974?（）.
单项选择题 Halon gas will decompose and may form very hazardous toxic fumes when discharged（）.