ILS机载接收机收到航向信标信号后,用哪个信号驱动航道偏离杆:().
A.90Hz调幅信号
B.150Hz调幅信号
C.用两个信号的“差信号”
D.用两个信号的“和信号”
参考答案:C
The steeper a firm's marginal revenue product curve for a given resource, the:()
A. more elastic the firm's demand curve for the resource.
B. less elastic the firm's demand curve for the resource.
C. higher the mobility of the resource.
野生动物要调查哪些内容()
A.种类
B.分布
C.迁徙路径
D.生境