由 have 加动词的过去分词构成,主语是第三人称单数时,要将have 改为has.
  例句:
  I have seen the film already. 我已经看过那部电影了。(现在我知道电影的内容了)
  Have you seen my bag?你看到我的手提包了吗?(你知道它在哪里?)
  She has been a dancer for ten years. 她已当了十年的舞蹈演员了。
  We‘ve planted thousands of trees in the past few years. 过去几年我们种了成千上万棵树。