12. Mrs. Quyen asked Mr. Long how long he had worked for that company (Câu gián tiếp WH_question: S + asked/wondered + (s.one) + S + V(lùi thì); have/has + p.p `->` had + p.p; you `->` he; this `->` that)
13. This room is not often used for meeting (Bị động HTĐ: am/is/are + p.p; we được lược bỏ trong câu BĐ)