低频25.7HZ的定义是什么？
参考答案：
载频切换信息码。
— There ________a football match on TV tonight. I can’t wait to watch it.
— Me, too. It’s ________ Guangzhou Evergrande and the Australian team Melbourne Victory.
A．will be; between
B．will be; both
C．will have; between
D．will have; both
线间距小于（）m时，禁止在正线与邻线间行走。
A.3.5
B.4.5
C.5.5
D.6.5
