天下雨时，你在干什么呢?
What________you________while it________ ________?
当他走进一家纪念品商店时，我很吃惊。
I was very________when he________ ________a souvenir shop．
你给我打电话时，我正站在图书馆的前面。
I________ ________in front of the library when you________ ________．
昨天晚上我妈妈很快就睡着了。
My mother________ ________soon last night．
（2014广东）Most people are________building a paper factory near here．They are worried the river will get polluted．
A．for
B．with
C．against
D．beyond
Yesterday evening I was playing the piano________the doorbell rang．
A．when
B．before
C．while
