21. — What do you think of the manager of your company?
— Oh, he is ______ manager who is pleasant to work with. It’s ______ pleasure to work with him.
A. the; the B. a; a C. a; the D. the; a
22. 1 have spent all my life living in my brother's shadow, ______hard for any possible way to show myself.
A. to search B. having searched C. being searched D. searching
23. He couldn't say exactly what it was______ bothered him.
A. which B. that C. it D. this
24.If you want to do the experiment again, you’d better be more careful ______ you have made a mistake.
A. where B. that C. why D. when
25. Such a chance, once ____, might never come again.
A. losing B. being lost C. lost D. to be lost