制备O/W型乳剂若采用的表面活性剂为乳化剂,适宜的表面活性剂HLB范围应为
A.8~18
B.7~9
C.3~6
D.15~18
E.1~3
参考答案:A
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An analog signal’s characteristic quantity representing data may (66) . at any instant, any value within a continuous (67) . For example, an analog signal may follow continuously the values of another physical quantity representing data.
A discrete signal is composed of (68) elements in time, each element having one or more characteristic quantities which can represent data. Examples of characteristic quantities are amplitude, waveform, (69) , and position in time. A digital signal is a special case of discrete signals, in which data are represented by a (70) number of well-defined discrete values that one of its characteristic quantities may take in time.
(66)处填()。
A.acquire
B.collect
C.assume
D.fetch