Across
- 3. a person who studies science
- 6. the study of the earth and its features
- 8. a period of school time
- 10. a mathematical value（用途)
- 11. the condition of being alive
- 12. not interesting
- 16. able to be used for a purpose（目的）
- 17. a difficult situation
- 19. a person who sings
- 20. causing great enthusiasm（热情）
Down
- 1. the study of past events
- 2. the language spoken in France
- 4. a device for making music
- 5. to keep in mind
- 7. the time before the present
- 9. very good
- 13. a cause for an action
- 14. the time yet to come
- 15. the study of living organisms（生物）
- 18. the use of supernatural powers