若系统是完全线性的,则输入-输出的相干函数一定为1。
参考答案:对
— I promise my daughter ____ get a nice present on her birthday.
— I think it will be a big surprise to her. [ ]
A. must
B. shall
C. might
D. need
散水一般坡度为()
A、1%
B、3%以下
C、3%~5%
D、5%以上