第21题: [单项选择]Prion的主要组成成分是() A. 核酸和蛋白质 B. 核酸、蛋白质和包膜 C. 活性蛋白质 D. DNA E. RNA 参考答案:C
第22题: [单项选择]Scuffed cylinder liner wearing surfaces in a diesel engines can result from () A. chromium plating piston rings B. knurling the piston skirt C. extended maximum power operation D. applying load to a cold diesel engine 参考答案:D