用所给单词的适当形式填空。
1. The children were ________ because they didn't get Christmas presents. (happy)
2. How can you make yourself ________ if you cannot express yourself clearly. (understand)
3. December is the ________ month of the year. (twelve)
4. The doctor's ________ made all of them sad. (dead)
5. I think this dictionary is ________ for your study. (help)
6. After a day's walk, she felt so tired that she couldn't go ________. (far)
7. Which river is the second ________ river in the world? (long)
8. It is a ________ for me to stay with you. (please)
9. They don't know why you talked to them so ________. (angry)
10. Someday you'll find a foreign language a bridge to a lot of ________. (know)
