从每题所给的A、B、C、D四个选项中，选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。
21. I don't think the experiment is _____ failure. At least we have got _____ experience for our
future work on _____ nature.
A. /; /; / B. a; /; the C. a; /; / D. /; the; /
22. — Dad, I'd like to go to the cinema with you.
— Sorry, dear, but the film is _____ adults only.
A. intended for B. made up of C. protected from D. taken in
23. The professor kept telling us that the future _____ to the well-educated and I kept wondering
where I _____ of it.
A. would belong; heard B. belonged; had heard
C. was belonged; heard D. was belonging; had heard
