FOR
For主要跟在下面这些名词的后面：
* a check for (amount of money)
例句: She gave me a check for $50.
她给了我一张50块钱的支票。
* a demand for something
例句: Unfortunately, there wasn't enough demand for our product.
不幸的是，我们的产品市场需求不大。
* a need for something
例句: There is a real need for discipline in this class.
这个班级，没纪律不行。
* a reason for something
例句: I have a reason for doing that!
我这么做是有理由的。
IN
In主要在下面这些名词后面：
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