The lecturer came into the hall，followed by a group of students.

　　＝The lecturer came into the hall，and he was followed by a group of students.

　　演讲者走进大厅，后面跟着一群学生。

　　5．有时分词前可以用连词加以强调。连词while常接现在分词；when 接现在分词或过去分词均可；once，if，though，although，even if，even though，unless，than，as 等只能接过去分词。有些过去分词作状语时，没有被动意味，只是表示一种状态或动作的完成。

　　When dressed in white，she looks really pretty.

　　穿上白色衣服，她看上去非常漂亮。

　　6．过去分词与现在分词作状语的区别：过去分词表完成、被动，与主句主语之间是被动关系；现在分词表进行、主动，与主句主语之间是主动关系。如果一个主动的动作发生在谓语动作之前，则可使用现在分词的完成时。

　　Shown around the city，we were impressed by the city's new look.

　　在城里走时，城市的新容给我们留下了深刻印象。

　　Seeing the picture，he couldn't help thinking of his good old days.

　　＝When he saw the picture，he couldn't help thinking of his good old days.

　　看到那张照片，他禁不住想起了美好的往昔。

　　Having finished their homework，the children went out to play football.

　　＝After the children finished their homework，they went out to play football.

　　做完作业后，孩子出去踢足球了。

　　即时跟踪1　用过去分词改写句子

　　1．When it is compared with the size of the whole earth，the biggest ocean doesn't seem big at all.

　　Compared__with the size of the whole earth，the biggest ocean doesn't seem big at all.

　　2．As he was frightened by the tiger，the boy didn't dare to go to the zoo alone.

　　Frightened by the tiger，the boy didn't dare to go to the zoo alone.

　　3．If these trees are grown in rich soil，they can grow faster.

Grown in rich soil，these trees can grow faster.