but, take place, in the past, go to work, used to be

Over the past ten years, great changes (1)_________ in our hometown. (2) ______, the houses in our hometown were very old, (3)_________ now most of the people have moved into tall buildings. The water in the river (4)_________ very dirty, but now the river is very clean, and we can swim in it. People here used to walk or ride bikes, but now they can take buses or drive their own cars (5)_________.