21. Darkness , so we had to stop our journey and stayed on a farm.
A. fell B. spread C. broke D. happened.
22. Life itself tells us it is necessary to learn to be .One can hardly survive without help from other people in the world.
A. sensitive B. competitive C. grateful D. careful
23. Bill Gates was so nice that he decided to ninety percent of his money to charities.
A. give up B. give away C. give out D. give off
