1.一般時:表示的動作與謂語動作同時發(fā)生。
When we arrived,we found him sleeping.我們到達時發(fā)現他在睡覺。
Living in the suburbs,we have few visitors.因為住在郊外,我們沒什么訪客。
2.完成時:表示的動作發(fā)生在謂語動作之前。
Having cleaned the desks,we began reading.擦完桌子后,我們便開始看書。
Not having finished his homework,the boy didn’t go to sleep.
因為沒有完成作業(yè),這男孩沒有睡覺。