2、先行詞有the only, the same, the very修飾時。
例如 The articles are the very ones that should be read.
3、先行詞有形容詞最高級和序數詞修飾時。
例如 This is the best film that I have ever seen.
4、先行詞既指人又指物。
例如 We talked about the person and things that we remembered.
5、句中已經有who或which時，避免重複。
例如 Who is the man that is making a speech?
只能用which，不能用that
1、在非限定性定語從句中，無論如何也不能用that
This brunch of carnation, which is wound by silk ribbon ,is the first gift to my mom.
這束康乃馨是送給媽媽的第一份禮物，它被絲帶所纏繞。
2、關係代詞前面出現介詞時
Those days in which you could travel without a passport has gone.
那些你不用帶護照可以旅行的'日子一去不復返了。
3、當先行詞本身為that（指代）時
what about that which had appeared in recent activities.
那個怎麼樣，在最近的活動中出現過. (結合具體語境看that所指代的是什麼)
4、當先行詞是baby, child等詞時
Have you notice that child which has lost his way to home in the supermarket ?
在超市，你注意到那個找不到回家路的孩子了嗎？
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