Sure, here are the sentences changed into passive form:

1. I was given mark 10 for my midterm test by the teacher.
2. The test is done well by Mai.
3. Tim was taken to the chocolate factory by his teacher yesterday.
4. Paper was made from wood pulp by a Chinese official in the year 105.
5. A car was rented by Vinh last week.
6. Who was the DNA discovered by?
7. When was the novel written by him?
8. Was paper pulp mixed with water by them?
9. Who was the fountain pen invented by?
10. The floor must be cleaned by the students every day.
11. The gate has just been repainted gray by our father.
12. A song was being sung by Alex when the doorbell rang.