数字调度通信系统里的磁石接口二线收为（）。
A.0dBr
B.-3.5dBr
C.-7.0dBr
D.-2.5dBr
参考答案：B
28. The reason for his success is ______ he worked very hard.
A．why
B．that
C．whether
D．How
什么叫地下水补给量？
