What is a valid CSS rule?

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4. What can CSS do?
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7. What is HTML CSS and JavaScript?
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Tags

1. #attribute
2. #valid
3. #validity
4. #interactive
5. #contain
6. #select
7. #selector
8. #determined
9. #evaluation
10. #pseudo
11. #meaning
12. #input
13. #level
14. #allows
15. #content
16. #elements
17. #defined
18. #based
19. #selectors
20. #style