单项选择题
The danger associated with using carbon dioxide in an enclosed space is（）.
A.frostbite B.skin burns C.asphyxiation D.an explosive reaction
单项选择题 The bottom row of plating next to the keel of a lifeboat is known as the（）.
单项选择题 The backup system on an electric start survival craft is a（）.
单项选择题 Symptoms of sea sickness include（）.
