She was playing the piano while I was reading the newspaper.

She was playing the piano while I was reading the newspaper.
可以变成She played the piano while I readed the newspaper.
什么情况过去进行时可以变成过去时`

可以
1.She hesitated for a minute and stood still while a tear or two fell on the worn red carpet.
她迟疑了一会儿,呆呆地站在那儿,同时一两滴泪水溅落在那破旧的红地毯上了.
2.“Della,”said he,“Let's put our Christmas presents away and keep'em a while….”
”他说“德拉,咱们把圣诞礼物收好,先保存一段时间.…”
这两句话中出现的while一词,用法不同.前一个作连词,意思为“与此同时”.后一个作名词,意思为“一会儿”.
为了帮助同学们更好地掌握此词在各种语境中的用法,现做如下总结：
一、while作名词用,表示“一会儿”“一段时间”
1.She likes to lie down for a while after lunch.
她喜欢午饭后躺一会儿.
2.Coming to another country to study requires a big adjustment and it takes a while to fit in.
来到另一个国家求学,需要花一段时间来适应.
二、While作连词
(1)引导时间状语
1.We must strike while the iron is hot.
趁热打铁.
2.While she was listening to the radio,she fell asleep.
她听着收音机睡着了.
(2)引起让步状语从句,意思是“虽然…但是….”、“尽管…但是…”(多放于句首)
1.While he loves his students,he is very strict with them..
虽然他爱他的学生,可是他对他们很严格.
2.While these experiments are interesting and useful,it is important to remember that they may not always tell us much.(BookIIIp125)
虽然这些实验很有趣也有用,但是很重要的是要记住,这些实验也可能不会告诉你很多.
(3)引起条件状语,意思是“只要”
1.While there is life there is hope.
只要生命存在,就有希望.
2.While there is a way there is away.
有志者事竟成.
三、While作并列连词用,意思为“而,然而”,表对比.而but表转折.注意用心比较体会while与but的句中用意
1.Some people waste food while others haven't enough.
有些人很费粮食,然而有些人却吃不饱.
2.The son was having a good meal at home,while the parents were working in the fields.
儿子在家吃好饭而父母却在田里辛勤劳作.
3.I ought to have helped her,but I never could.
我本该帮她但没能.
4.Honey is sweet,but the bee stings.
蜂蜜很甜,但蜜蜂有刺蜇人.
四.while,when,as的用法区别
都译为“当…的时候”,区别为：when后的从句谓语动词既可是延续性动词,也可是短暂性动词,而且还可作并列连词,译为“这时”.但以下句型一定用when,作并列连词：
句型A：be about to do…when…正要做…这时(发生另一事)
句型B：was/were doing…when…正在…这时(发生另一事)
句型C：had done…when…刚要做…这时(发生另一事)
1.We were about to set out when it began to rain.
我们刚要出发天突然下雨了.
2.He had hardly sat down when his mobile rang.
他刚一坐下手机就响了.
3.I was walking along the bank of the river when I fell into it.
我正沿河岸散步突然掉进水里.
while后的从句谓语动词只能是延续性动词,强调主从句的两个动词同时发生；while也可作并列连词,表示两个动作的对比,译为“而”“然而”.as则表示两个变化中的动作的同时性,译为“一边…一边…”.
1.While his mother was cooking in the kitchen,the boy fell asleep in the chair.
(在一个延续动作过程中发生另一个动作)
2.He hurried home,looking behind as he went.
他匆匆回家,边走边往后看.