表面活性剂用于固体分散体的载体，正确的叙述是（）

A.在水和多数溶剂中溶解，载药量高

B.可阻滞药物结晶析出

C.形成界面

D.较低的熔点适于熔融法制备固体分散体

E.低毒性

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.

（90）是（）

A.small

B.limited

C.infinite

D.finite