估计成本的目的是为了确定产品价格的下限。
参考答案:对
—Do you __________ the idea of living a low-carbon life?
—It sounds tough, but it is a tendency. [ ]
A. correspond to
B. apply to
C. cater to
D. subscribe to
产生调频信号的方法较多,但大多数采用()调频和间接调频。