记录到数码摄像机的摄像带上的信号是数字信号。( )
参考答案：错
The two naughty boys were quiet when eating, and they were accustomed to ______ at meals.
A．talk
B．talking
C．not to talk
D．not talking
上证成分股指数也叫做（）。
A．上证综合指数
B．上证180指数
C．上证30指数
D．上证红利指数
