Điền vào chổ trống

21.Alice (hurt)……….. herself while she ……………………. (skate). 
22. I (meet)……….. my neighbor while I ……………………………. (walk) home from work. 
23. Sally (see) ………….a friend while she ………….. (ride) her bicycle along Park St. 
24. Peter (fall)……….. asleep while he …………………………………… (study). 
25. Bob stepped on Jane‟s feet while they ………………….. (dance) together. 
26. I cut myself while I… (shave). 
27. Mr. and Mrs. Brown burned themselves while they …………… (bake) cookies. 
28. Tommy had a nightmare while he ……………….. (sleep) at a friend‟s house.