一.单项选择（15分）
（ ）21. --_____ do you study for a test?
--_____ reading the textbook.
A. What; On B. How; By C. What; By D. How, on
（ ）22. I don't know _____ this problem. It's too hard.
A. which to do B. how to deal with C. what to deal D. How deal with
（ ）23. Are you afraid of _____ alone?
A. sleep B. to sleep C. sleeping D.slept
（ ）24. I _____ half an hour doing my homework yesterday.
A. spent B. paid for C. took D.cost
