21. When you finish reading the book, you will have ______better understanding of______ life.
A. a; the B. the; a C. /; the D. a; /
22. Development of science and technology must benefit people ______ harm them.
A. rather than B. other than C. more than D. better than
23. It was impolite of him ____without ____good－bye
A. to leave; saying B. leaving; to say C. to leave; to say D. leaving; saying
