电视机屏幕上出现水平一条亮线，原因可能是（）。
A．高频头
B．亮度通道
C．行扫描电路
D．场扫描电路
参考答案：D
The first use of atomic weapons was in 1945, and their power _____ increased enormously ever since. [ ]
A. is
B. was
C. has been
D. had been
下列历史事件，与孙中山无关的是[ ]
A．创立兴中会和同盟会
B．就任中华民国临时大总统
C．参加中共“一大”
D．主持国民党“一大”创立黄埔军校
