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（）.

单项选择题 Goods of an inflammable，explosive or dangerous nature to the shipment whereof the carrier，master or agent of the carrier，has not consented，with knowledge of their nature and character，may at any time before discharge，（）at any place or destroyed or rendered innocuous by the carrier without compensation.