过去进行时常见的标志性时间状语主要有：this morning、the whole morning、all day、yesterday、from nine to ten last evening、when、while、at that time等
一、现在分词
1.在动词原形后直接加-ing
look-looking cook-cooking read-reading
2.以不发音字母e结尾的动词 ，去掉e再加-ing
write-writing live-living
3.以重读闭音节结尾且末尾只有一个辅音字母的动词，双写该辅音字母后再加-ing
begin-beginning swim-swimming sit-sitting
4.少数几个以ie结尾的动词，要变ie为y，再加-ing
tie-tying die-dying lie-lying
二、时间状语
this morning,the whole morning,all day,yesterday,from nine to ten last evening,when,while,at that time.
例句：
My brother fell while he was riding his bicycle and hurt himself;
When I got to the top of the mountain,the sun was shining.
