1 . 单句改错
1. Late although it was, we still went on working.
2. Although he is over eighty, but he looks healthy and energetic.
3. As they are poor, they are happy.

2 . 单句改错
1. All of a sudden, a boy ran into him, making some food drop on his trousers, what I thought would make him annoyed with the boy.
2. I shall never forget the years I spent in the country with the farmers, that has a great effect on my life.
3. I also enjoyed the evenings when we spent together.
4. The visitors saw rows of houses, the roofs of whose are red.
5. Please tell me the way which you did the job.

3 . 单句改错
1. They say they have learned what is not taught in textbooks and have got a great deal practice.
2. Hope you reply me soon.
3. If you find a position at there, I'm sure you'll have a rapid improvement in both your character and ability.
4. In Sunday morning, Li Lin was about to study when his father came up and advised him to have a break.
5. We cannot exchange money into friendship or love.