The police catch (抓住) many ________ every year. [ ]
A. thieves
B. thief
C. thiefs
答案:A
不属于X线管组件散热方法的是()
A.密封管套,自然散热
B.密封管套,风扇散热
C.闭路油循环风冷散热
D.管套内冷水循环散热
E.空调散热
何谓“频率崩溃”现象?