用方框中所给单词的适当形式填空。（每小题1分，共5分）

pour  seem  large  rapid  pollute

小题1:It ____________ that their living conditions were not very good.  
小题2:In the past twenty years, my hometown has developed ____________.
小题3:Our government has taken action to make the ____________ river clear again. 
小题4:There are several small chemical factories ____________ waste water into the river. 
小题5:At that time, China was the country with the ____________ population in the world.