What’s wrong with you yesterday—When I was playing football, my strength___________ and I fell down.

t countries, urban population is ____while the population of German ___ by 8 percent.

Which one do you want to buy, anipod touch 4, an ipad 3 or an iphone 5 ?—______. They are too expensive.

In modern times, the development of science is ________ .

The building project __________ next year is not easy __________in time.