视频系统的输入输出格式是指视频接收、处理和传送信号的方式。( )
参考答案：对
When I talked with my grandma on the phone, she sounded weak, but by the time we ____ up, he voice had been full of life．
A．were hanging
B．had hung
C．hung
D．would hang
刺激引起兴奋的基本条件是使跨膜电位达到（）。
A.阈电位
B.峰电位
C.负后电位
D.正后电位
E.局部电位
