21. What I need is _____ book that contains ______ ABC of oil painting.

A.    a; the        B. the; /         C. the; an       D. a; the

22. Compared with his sister, Peter is even more_______ to, and more easily troubled by, emotional and relationship problems.

A. skeptical      B. addicted       C. accessible     D. sensitive

23. ______the lecturer more clearly, I arrived early and chose a front seat.

A. Hear         B. Hearing       C. Heard        D. To hear