新中国诞生前后，中国人民解放军进一步发展壮大，其标志是

A．组建了中国人民解放军导弹部队

B．成立了中国人民解放军海军和空军

C．爆炸了第一颗原子弹和氢弹

D．发射了“长征一号”运载火箭

Although a given waveform may contain frequencies over a very broad range, as a practical matter any transmission system will be able to accommodate only a limited band of (86) . This, in turn, limits the data rate that can be carried on the transmission (87) A square wave has an infinite number of frequency components and hence an infinite (88) However, the peak amplitude of the kth frequency component, kf, is only l/k, so most of the (89) in this waveform is in the first few frequency components. In general, any digital waveform will have (90) bandwidth. If we attempt to transmit this waveform as a signal over any medium, the transmission system will limit the bandwidth that can be transmitted.

（86）处是（）

A.frequencies

B.connections

C.diagrams

D.resources