教科书上说 be going to 表示“事先已做好安排”，如何用这种说法来解释“She's going to be sick.”?
be going to 除了具有“将要”“准备”“打算”这些基本含义之外，还可表示“预计要发生”“不可避免会发生”这层含义。R. Quirk 等人把这层含义称作“future result of present cause”（现在原因的将来结果）。一般地说，这里的预计或预断并不是凭空做出的，而是根据目前的某种迹象做出的。用于这种含义的 be going to，其主语既可以是指人的，也可以是指物的。例如：
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You're going to have trouble with that car before long. (Wood) 你使用这辆车不久就会遇到麻烦的。
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We're going to die some day. 我们总有一天会死的。
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I'm going to be fifty next month. 下个月我就50岁了。
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She's going to have a baby. 她要生孩子了。
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She's going to be sick. 她要生病(呕吐)。
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I think it's going to rain. 我看天要下雨了。
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There is going to be a thunderstorm. (Wood) 要来雷雨了。
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I mean to go, and nothing is going to stop me. (URW) 我想走，什么事情也阻止不了我。
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Kennedy was going to be President whether we liked it or not. (Hillary, Living History) 肯尼迪就要当总统了，不管我们是喜欢还是不喜欢。