请问can和could有什么区别?

请问can和could、may和might有什么区别 can&could有什么区别? can have done和 could have done有什么区别? you can stay和you could stay有什么区别 can may could 有什么区别 can you；could you有什么区别? 请问could,would有什么区别? 情态动词表肯定推测时,might和may,could和can之间有什么区别?might和could呢? I could kill you 和I can kill you有什么区别? could have done 和 can have done 有什么区别?还有would have done 英语里could和can有什么区别,分别在哪里使用 could和can的区别