may have been和may be有什么区别?

may have been和may be有什么区别? could have been 和may have been 有什么区别? might be和 may have been的区别?还有是might do和 may have done 请问May be 和May have been 的区别,它们分别在什么时候用? maybe 和may be 有什么区别 may have been 和may have done的区别,特别是may have been doing和may h may,may be,might都有什么区别,和用法上有什么区别. may have done sth 和might be 都是表示对过去的猜测 有什么区别? be likely to do sth ,have an ability to do sth和may有什么区别 there may not be 和 there may be no有什么区别? may be和maybe用法有什么区别? He may have been busy和He might be busy