单项选择题
Portable carbon dioxide fire extinguishers should be sent ashore to be recharged （）.
A.when the remaining charge volume is less than 90 percent of the required VOLUME B.at each inspection for certification C.at each annual inspection D.when the weight loss exceeds 10% of weight of charge
单项选择题 The lengthening of a crack formed in the shell plating of a ship may be prevented by （）.
单项选择题 The fire extinguishing action of CO2 comes mostly from （）.
单项选择题 The amount of expansion space to be left in a fuel tank when fuel oil is being received, is determined by the （）.
