用所给词的适当形式填空。
l. Don't play while _____ (eat).
2. It's_____ (usual) for a 7-year-old boy to work out the difficult problem.
3.Who jumps_____ (high)in your class?
4. Why don't you try_____ (ride) a bike to go to school?
5. Keep_____ (work) hard until you make it.