Viết lại câu sao cho nghĩa ko thay đổi
1. These students had a lot of homework that they had to do
-> These student had......
2. There was no place where we could sit (us) 
-> There.......
3. He worked out the answer. It was clever of him
It was......
4. He crossed the road hurriedly. I caught sight of it
-> I noticed.....