21. --- I hear Jane has gone to the Holy Island for her holiday ?
--- Oh, how nice ! Do you know when she __________ ?
A. was leaving B. had left C. has left D. left
22. I first met Lisa three years ago. She _______at a clothes shop at the time.
A. has worked B. was working C. had been working D. had worked
23. You shouldn’t accept a gift from a person _____ you don’t know him.
A. until B. unless C. if D. whether
