A 形式

　　to have been+现在分词：

　　He seems to have been spying for both sides.

　　他似乎一直在为两方面搞秘密情报。

　　B 用法

　　主要用于助动词之后和appear，seem之后，但也可以用在happen， pretend以及believe， know， report， say， understand的被动式之后：

　　He says he was talking to Tom.

　　He couldnt have been talking to Tom.Tom wasnt there.

　　他说他当时在跟汤姆说话。

　　他当时不可能在和汤姆说话。汤姆当时不在那里。

　　I was following Peter closely.

　　You shouldnt have been following him closely;you should have left a good space between the two cars.

　　当时我正紧紧地跟着彼得。

　　你不应该紧跟着他;而应该使两车之间保持相当的距离。

　　He appears to have been waiting a long time.相当于：

　　It appears that he has been waiting a long time.

　　看来他已经等了很久了。

　　He pretended to have been studying.相当于：

　　He pretended that he had been studying.

　　他假装一直在学习的样子。