5. The fire alarm is tested by the electricians.
- Bị động thì HTĐ: is/am/are + PII+ (by O)
7. The cat was not bitten by the dog.
- Bị động thì QKĐ: was/were + PII+ (by O)
9. The bathroom was cleaned by John.
- Giải thích như câu 7.
10. Photos are taken by Frank.
- Giải thích như câu 5.