What do question marks mean in crosswords?

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Tags

1. #appear
2. #usually
3. #question
4. #answers
5. #three
6. #inform
7. #leave
8. #marks
9. #signals
10. #answer
11. #puzzle
12. #related
13. #things
14. #words
15. #clues
16. #several
17. #gently