X线管中，阳极靶面的作用是（）
A.散热
B.发生X线
C.阻止高速电子
D.完成高压电路的回路
E.产生电子流
参考答案：B, C, D
Su Lijie, 39-year-old female graduate of Peking University’s graduate school ended up ____as a house painter back in her hometown.
A．to work
B．worked
C． being worked
D． working
当总供给大于总需求时，会出现( )等现象。
A．生产能力闲置、通货紧缩B．失业增加、通货膨胀C．市场供应紧张、通货膨胀D．物资匮乏、通货紧缩
