They "customize" their books by engagingwith different layers and linkages.
他们通过加入不同的层次和连接部分“定制”了自己的书。
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Experts observe that "textbooks come in layers, something like an onion". For an active learner, engagingwith a textbook can be an interactive experience.
Over the years, many scholars have insisted that time online does not necessarily take away time spent engagingwith traditional media or on other activities.