21. Neither he nor I ________ able to persuade her to change her mind.
A. is B. are C. were D. am
22. You should try to get a good night's sleep _____ much work you have to do.
A. However B. no matter C. although D. whatever
23. When I got to the ticket office,all the tickets _____.
A. were sold out B. have been sold out C. had been sold out D. had sold out
