Why can't I scroll up and down on my Mac?

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Tags

1. #first
2. #preferences
3. #three
4. #apple
5. #select
6. #system
7. #general
8. #click
9. #based
10. #under
11. #screen
12. #always
13. #options
14. #automatically
15. #scroll
16. #heading
17. #scrolling
18. #device
19. #input