这种问答题在做阅读理解中较为少见,我们一般用标准化 ABCD 选项,做起来没有第二个答案.回答问题时,同样的意思可以用不同的词语表达,而且字数也不一样,此外还会出现不同的理解,这本身很正常,所以我下面的参考答案可能与原题的答案不一样,而且也可能与他人的用词有区别.至于答题技巧,你看懂了就能回答,没看懂就无法回答,实在没有什么技巧可言,唯一的一点是理解原文,尊重原文,到原文中找依据.
17. No, he isn't. （原文第一句话是依据）
18. It means "to drink down eight glasses of water daily".（原文第3行）
19. (The old "8-a-day" rule is for) people under difficult situations, for example, soldiers at high altitude / hospitalized patients, （原文最后一句话是依据,两个例子只要写一个）
20. You need what you need. Everybody needs different amount of water depending on their situations.
21. It is about how much water a person needs every day. The idea to drink eight glasses of water daily is out of date. A person just needs to drink water when he needs water, that is to say, drink water when you feel thirsty.
希望以上解释对你有所帮助.祝进步.