请问can和could有什么区别?

请问can和could有什么区别? 请问can和could、may和might有什么区别 can和could的用法?can和could有什么区别?什么时候用哪个? can may could 有什么区别 could与 can有什么区别? could和can的区别他们的用法有什么区别啊,什么时候用can,什么时候用could呢? you can stay和you could stay有什么区别can 和 could 有什么区别?用法也有什么区别? can have done和 could have done有什么区别?那can have done什么用法？ 请问could,would有什么区别? could have done 和 can have done 有什么区别?还有would have done I could kill you 和I can kill you有什么区别? I can be the one和I could be the one有什么区别 can you tell me 和could you tell me 语气上有什么区别? i could take you up和i can take you up 有什么区别.求详解. can 和could 在疑问句中的区别比如有时候说can i have a day off?有时候说could i have the bill?两者有什么区别吗 请问could和would在虚拟语气中有什么区别?请问could和would在虚拟语气中有什么区别. could与can,might与may有什么区别? can could 在疑问句中有什么区别?