1）have +过去分词，构成完成时态，例如：
He has left for London.　他已去了伦敦。
By the end of last month, they had finished half of their work.　
上月未为止，他们已经完成工作的一半。

2）have + been +现在分词，构成完成进行时，例如：
　 I have been studying English for ten years.
　 我一直在学英语，已达十年之久。

3）have+been +过去分词，构成完成式被动语态，例如：
　 English has been taught in China for many years.
　 中国教英语已经多年。