507. What are in your mind at the moment?

508. It was Mary that rang hours and hours ago.

509. We had no difficulty (in) finding the house. (TA mới ngta ko dùng"in" nữa)

510. The exhibition has not been so well attended this year.

511. I might have known that my children wouldn't like the new, cheaper ice-scream.

512. Make sure you finish tying all these letters before going to lunch.

513. Only then that moment did he realise how much he loved her.

514. Until I tell you, you cannot leave.

515. If I were you, I would go by train.

516. Through no fault of mine that the business failed.

517. David was instrumental in drafting the proposal.

518. If you had stuck to our original agreement, everything would have been fine.

519. When I heard her speak, it made a profound impact on me.

520. No rain in Ha Noi since 1984 was as big as the one last October.

507. What are you thinking at the moment?
→ What are in your mind at the moment?
508. Mary rang hours and hours ago. (THAT)
→ It was Mary that rang hours and hours ago.
509. It was easy for us to find the house.
→ We had no difficulty in finding the house.
510. Attendance at the exhibition has been down this year.
→ The exhibition has not been so well attended this year.
511. It shouldn't have surprised me that my children didn't like the new, cheaper ice-scream.
→ I might have known that my children wouldn't like
512. Don't go to lunch until you have typed all these letters.
→ Make sure you finish tying all these letters before going to lunch.
513. He didn't realize until that moment how much he loved her.
→ Only then that moment did he realize how much he loved her.
514. You can leave only when I tell you.
→ Until I tell you,  you cannot leave.
515. I think you should go by train. (WERE)
→ If I were you, I would go by train.
516. It wasn't my fault the business failed.
→ Through no fault of mine that the business failed.

517. David played the main role when the proposal was drafted. (INSTRUMENTAL)
→ David was instrumental in drafting the proposal.

518. If you hadn't changed our original agreement, everything would have been fine. (STUCK TO)
→ If you had stuck to our original agreement, everything would have been fine. 

519. When I heard her speak, it affected me profoundly. (IMPACT)
→ When I heard her speak, it made a profound impact on me.

520. The rain in Ha Noi last October was the biggest one since 1984.
→ No rain in Ha Noi since 1984 was as big as the one last October.