Change these sentences into the active voice: (Chuyển các câu sau sang câu chủ động)
1. Oil is obtained from under the ocean by workers.
2. A big house is being built in this garden by the family.
3. The cart was drawn by horses.
4. They will be helped by that kind woman.
5. Grass is eaten by cows and buffaloes.
6. The lesson was explained by the teacher.
7. Grammar is taught by Mr. Brown.
8. A hole was being dug in the garden by him.
9. Coffee is being made by the maid.
10. The box will be moved away from the window by us.
11. This tree was plainted by my grandfather.
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