四级考试常用语法精选（4）

　　to do

　　完成式

　　to have been done

　　to be doing

　　完成进行式

　　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之前发生, 就要用不定式的完成式.

　　I am glad to have seen your mother .

　　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 havent quite recovered yet.

　　We didnt 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.