21. They don't come to the book club any more, for _______ reasons or other.
A. some B. all C. either D. both
22. You _____ bring your identification when you open a bank account.
A. may B. can C. must D. will
23. After the accident, we are _____concerned with the safety of school buses than we used to be.
A. little B. less C. much D. more
