Across
- 3. helpful or practical
- 5. full of fun and interest
- 8. the study of past events
- 9. the study of living things
- 11. a person who studies science
- 14. special power to make things happen
- 16. to keep in mind
- 18. very good
- 19. in the role of
- 20. time gone by
Down
- 1. something difficult to solve
- 2. time yet to come
- 4. a person who sings
- 6. the time when a person is alive
- 7. not interesting
- 10. a device for making music，like piano,violin and so on
- 12. a symbol used in counting
- 13. a period of school time
- 15. the study of the earth and its features
- 17. why something happens