单选题 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 ______. This, in turn, limits the data rate that can be carried on the transmission ______. A square wave has an infinite number of frequency components and hence an infinite ______. However, the peak amplitude of the kth frequency component, kf, is only l/k, so most of the ______ in this waveform is in the first few frequency components. In general, any digital waveform will have ______ 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.