1. never trouble trouble till trouble troubles you.

　　麻煩沒來找你，就別去自找麻煩。

　　第一、四個trouble是動詞，第二、三個trouble是名詞。

　　2. i think that that that that that student wrote on the blackboard was wrong.

　　我認為那個學生寫在黑板上的那個“that”是錯誤的。

　　第一個that是連詞，引起賓語從句；第二、五個that是指示代詞“那個”；第三個that在這兒相當  于名詞；第四個that是關系代詞，引起定語從句。

　　3. i know. you know. i know that you know. i know that you know that i know.

　　我知道。你知道。我知道你知道。我知道你知道我知道。