拓展：have been，has been， had been
1.解釋：have/has/had+been 都是完成時。
2.區別：has/have been是現在完成時,has用於第三人稱單數; had been過去完成時,跟前者相比,比前者更爲過去;
3.例句：
（1）He has been doing this work for a period of time.
（2）I want to have this book.
（3）Have you pass the math exam?
（4）Do you ever had a thought that you can win this game?
