7. That skateboard was bought by John 3 years ago.
→ bị động QKĐ: S + was/were (not) + V3/ed + (by+O) + time
8. Those letters were sent to me by my friends.
→ bị động QKĐ
9. The TV was moved in to Alex's room by him.
→ bị động QKĐ
10. Flour is always used for making cake.
→ bị động HTĐ: S + is/am/are (not) + V3/ed + (by+O) + time