Sửa lỗi sai

Sửa lỗi sai:
1, "Could you help me lift this box?" Of course I did"
2. I could go to Emma's party last Saturday.
3. May these flower be from your fiancé?
4. Although she was exhausted, she could finish the race.
5. I must have my car repaired last month.
6. The bus can be late because there is a lot of traffic .