United,we stand;divided,we fall.

(If we are united...)(表条件)

团结则存，分裂则亡。

Having been shown around the library,we came to the classroom building.

(After we were shown around...)

参观了图书馆后，我们来到了教学楼前。（表时间）

Once seen,it can never be forgotten.

(Once it is seen...)

一旦被看见，就永远不能忘记。

【知识小结】

过去分词作状语可表时间、地点、原因、条件、让步、伴随等情况，这种过去分词相当于一个状语从句，其句子的主语和分词之间有被动关系。

活学巧用

3.单项填空

（1）When first ________to the market,these products enjoyed a great success.

A.introducing B.introduced

C.introduce D.being introduced

答案:B

（2）________by the beauty of nature,the girl from London decided to spend another two days on the farm.

A.Attracting B.Attracted

C.To be attracted D.Having attracted

提示："因为被自然的美景所吸引，女孩决定再呆两天。"过去分词作状语，相当于原因状语从句。

答案:B

（3）Unless________to speak,you should remain silent at the conference.

A.invited B.inviting

C.being invited D.having invited

提示："除非你被邀请讲话"，采用过去分词作条件状语，表被动。相当于unless you're invited...。

答案：A