主动形式                         被动形式
一般式 to do                            to be done
完成式 to have done               to have been done
进行式 to be doing   
完成进行式 to have been doing   
  

    完成式: 不定式的一般形式所表示的动作, 通常与主要谓语表示的动作(状态)同时(或几乎同时)发生, 或是在它之后发生. 假如不定式所表示的动作, 在谓语所表示的动作(状态)之前发生, 就要用不定式的完成式.
   
    I am glad to have seen your mother (= I am glad I have seen your mother).
   
    (比较: I am glad to see you.)
   
    He is said to have written a new book about workers.
   
    He pretended not to have seen me.
   
    进行式: 如果主要谓语表示的动作(状态)发生时, 不定式表示的动作正在进行, 这时要用不定式的进行式.
   
    You are not supposed to be working. You haven’t quite recovered yet.
   
    We didn’t expect you to be waiting for us here.
   
    He pretended to be listening attentively.
   
    完成进行式: 在谓语所表示的时间之前一直进行的动作, 就要用不定式的完成进行式.
   
    The struggle was known to have been going for twenty years.
   
    We are happy to have been working with you.