After two hours of walking, they came to the camp site, ______ .
8.Customers are asked to make sure that they ____ the right change before leaving the shop.
7.Although the causes of cancer ____, we do not yet have any practical way to prevent it.
6.I have to go to work by taxi because my car ____at the garage.
5.―Have you handed in your schoolwork yet? ―Yes,I have. I guess it ____ now.
4.It is said that the early European playing-cards ____ for entertainment and education.