1. He asked how many lessons I was going to learn the next month.

Câu gián tiếp: S1 + asked + O + Wh + S2 + V_(lùi thì)

2. This is the first time I have traveled by plane.

3. If I had gone shopping, I could have bought that sweater.

Câu điều kiện loại 3, giả định điều không có thật ở quá khứ: If + S + had V_P2, S + would/ could + have V_P2

4. He had difficulty in starting the car.

to have difficulty in V-ing: gặp khó khăn với

5. David was so ill that he couldn't go camping with us.

so...that = too...to: quá đến nỗi mà

6. Our teacher speaks too small for us to hear.

7. Peter hasn't been seen since the day of the party.

No one mang nghĩa phủ định

=> Chuyển sang câu bị động như trên

8. The fog prevented us from driving.

prevent...from + V-ing: ngăn cản, cản trở làm điều gì

9. It took us more than three hours to fly to London.

It + takes + ... + time + to V: nó tốn bao nhiêu thời gian để làm gì

flight (n) chuyến bay -> fly (v)