Web page addresses have to be both lengthy (key words help search-engine rankings) and terse (to be snappy and memorable, and to fit on Twitter).
网址必须既有一定的长度（关键词有助于搜索引擎排序），又必须精简（短小精悍让人过目难忘，并且适合在Twitter使用）。
Even writing down a few key words will help you remember the main point of the idea.
即使只记下几个关键词也能帮你记起大概的想法。
In the section of Mastering New Words, the authors use simple sentences to help the learners to understand the key words in the texts.
攻克生词部分以简单自然的语句练习帮助学生理解文中出现的重点词语；
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