1. Never trouble trouble till trouble troubles you. 麻烦没来找你,就别去自找麻烦。
第一、四个trouble是动词,第二、三个trouble是名词。
2. I think that that that that that student wrote on the blackboard was wrong. 我认为那个学生写在黑板上的那个"that"是错误的。
第一个that是连词,引起宾语从句;第二、五个that是指示代词"那个";第三个that在这儿相当于名词;第四个that是关系代词,引起定语从句。
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。
4. We must hang together, or we'll be hanged separately. 我们必须团结在一起,否则我们将被一个个绞死。