系统中引起谐振过电压原因是多方面的,下面( )不是引起谐振过电压的原因。
A.设备绝缘配合错误; B.系统故障;C.元件参数组合不利; D.操作不当。
参考答案:A
消化系统常用的X线检查()
A.腹部平片
B.钡餐或钡灌肠
C.X线胆道造影
D.腹腔动脉造影
E.CT
— Are you going to buy a camera?
— Yes. But there are so many kinds that I can't decide _____ to buy. [ ]
A. what
B. which
C. how
D. where