单项选择题
Compared to the amount of concentrated foam liquid used，the amount of low expansion mechanical foam produced is（）.
A.97 times greater B.94 times greater C.10 times greater D.2 times greater
单项选择题 Combustible gas indicators operate by drawing an air sample into the instrument（）.
单项选择题 Butadiene，inhibited，is labeled as a（）.
单项选择题 Before starting a gasoline engine on a motorboat，you should make sure for safety that（）.
