1. Tim is at the same age as Hoa.
-> bỏ at
2. At recess, the students practice to play basketball.
-> to play -> playing
3. Do you know how much a banana cost?
-> cost -> costs
4. The teacher says Ba will be a famous artist in one day.
-> bỏ in
5. Some boys are playing marble in the school yard at recess.
-> marble -> marbly
6. Some students are playing game as blind man's buff and catch.
7. Mai learns how to use a computer in her scientific class.
-> scientific -> computer
8. I'd love coming to your birthday but I'm much to busy.
-> coming -> to come
9. There are less TV programs for teenagers than there are for adults.
-> less -> more
10. People are living longer so there are more and more many old people.
-> bỏ many