À vâng.

7. By the time I finished all my work, Ben had arrived.

8. By the time I went to the supermarket, I had prepared dinner for my family.

I am spending a week at a summer camp.

*Spending+Time+...+Something: Dành thời thời gian cho thứ gì đó

Oke ạ. Sửa:

7.By the time I had finished all my work, Ben arrived.

8.By the time I had gone to the supermarket, I prepared dinner for my family.

Passive voice (bị động) phải không?

1.Where are these books not allowed to be taken by Tom?

2.Why wasn't the science conference canceled by you?

3.Why wasn't he helped with the crane by them?

5.When I left the house this morning, I didn't have breakfast.

6.After I finished all my work, Ben arrived.

7.By the time I finished all my work, Ben arrived.

8.By the time I went to the supermarket, I prepared dinner for my family. 

9.Before Mr. Brown returned home as an excellent engineer, he studied abroad for four years.

10.Before my brother felt a little bit better, he drank some orange juice.

Câu 4. you+were

2.When I entered the room, I was surprised by what I saw.

3.The rain prevented the volunteers from mowing the old lady's lawns.

4.After David finished his homework, he went to bed.

I suggest going for a walk in the park.