提取文字：

Generally, this means two or three paragraphs, arranged as shown in Exhibit 11. The Situation and the Complication can each be as long as three or four paragraphs, but never more than that. It can't take very much to remind someone of what he already knows. Indeed, if you find yourself littering the introduction with exhibits, you can be sure that you are overstating the obvious.

By contrast, the introduction can also be as short as a sentence: ‘In your letter of January 15 you asked me whether…’ The closer you are in your everyday dealings to the person to whom you are writing, the shorter the introduction can get. But it must say enough to remind the reader of his Question.

翻译：

通常，这意味着引言有两到三个段落，按照附件 11 所示的方式排列。情境和复杂情况每部分可以长达三到四个段落，但不能超过这个长度。提醒他人已经知道的内容不需要很多话。实际上，如果你发现引言中充满了附加说明，那么可以确定你在强调显而易见的内容。

相比之下，引言也可以短至一句话：“在您1月15日的信中，您询问我是否……”你与读者在日常事务中的关系越密切，引言就可以越短。但必须要有足够的信息来提醒读者他的问题。