Since the mid-1990s, online sales have been__________ (增加)by over 25% per year.
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It can also be __________ ( 便利的) very to do your shopping from home, day or night.
With “Click and Collect,” the customer can order online and his order is __________ (递送到) to a store in his neighbourhood.
It now seems clear that Internet shopping is not going to __________ (取代) traditional retailing.
能生成鞣红的最根本原因是( )
A. 鞣质与空气接触
B. 鞣质在水中久置
C. 鞣质在酸性条件下加热
D. 缩合鞣质的缩合性
E. 可水解鞣质的水解性