Giúp mình với mình đang cần gấp hữa vote 5 sao

Ex2: Supply the correct verb forms. 1.I (see) a car accident while I (wait) for you on this corner yesterday. 11.Up to then I never (see) such a fat man. 12. I (not see) him since last Monday. 2.Mr Jone (be) principal of our school since last year. 13. They had sold all the books when ...