21. Nobody knows the man killed in the accident, so it is difficult for the police to find out his ___________.
A. thought B. height C. weight D. identity
22. If you want to speak good English, a large _____ is needed.
A. spelling B. vocabulary C. practice D. memory
23. —Hello! Is Mr. John in the office?
—Yes. But I’m sorry. He is busy _____ and can’t speak to you.
A. at once B. at present C. at the end D. at first
