要使一个频带受限于BHz的信号S（t）从取样后的信号无失真地恢复出来，取样频率fs必须满足fs≥2B。
参考答案：对
This is my new pen. It_____ me 18 yuan. [ ]
A. cost
B. spent
C. paid
D. took
A．风力水平向左
B．风对物体做负功
C．风对物体做功为零
D．物体机械能减少mg2t2/2
