现在完成时的结构；助动词have /has + 动词的过去分词.
He has been to Beijing.
I have had supper .
He has read the book.
She has finished her homework.
Jim has done his homework.
He has finished the work.
We have been friends for ten years.
He has taught in this school for two years .
The fish has been dead for three hours .
The dog has eaten the food .
They have gone home .