单项选择题
Before you begin administering artificial respiration, you should be sure the victim（）
A.is comfortable B.is warm C.is not bleeding D.has a clear airway
单项选择题 If liquid freon should come in with your skin, you should （）
单项选择题 If the effective bearing area has been reduced , remedial action should be taken（）
单项选择题 Main diesel engine control can be obtained by the bridge （）
