to do

　　完成式

　　to have been done

　　to be doing

　　完成進行式

　　完成式: 不定式的一般形式所表示的動作, 通常與主要謂語表示的動作同時發生, 或是在它之后發生. 假如不定式所表示的動作, 在謂語所表示的動作之前發生, 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.

　　進行式: 如果主要謂語表示的動作發生時, 不定式表示的動作正在進行, 這時要用不定式的進行式.

　　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.

　　完成進行式: 在謂語所表示的時間之前一直進行的動作, 就要用不定式的完成進行式.

　　The struggle was known to have been going for twenty years.

　　We are happy to have been working with you.