Clue for the first key

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Across
  1. 3. When a place is full of people it's "...".
  2. 5. The animal on the Welsh flag
  3. 6. Neil Armstrong was the first "..." on the moon.
  4. 11. If you don't think somebody is right, you "..." "..." that person.
  5. 14. If you don't listen to what your parents say, you "..." them.
  6. 16. If you really need something to drink, you're "...".
  7. 17. Some spiders can kill you because they're "...".
Down
  1. 1. When you visit a school in another country for a short time, you're an "...".
  2. 2. Inside a "..." you can find important sights of a city.
  3. 4. To say sorry
  4. 7. The opposite of "strong"
  5. 8. Necklaces, rings, earrings, bracelets, ...
  6. 9. The opposite of "life"
  7. 10. What you put inside of a turkey
  8. 12. The opposite of "to marry"
  9. 13. Chips, crisps, fries: they're all made of "...".
  10. 15. Criminals often "..." other people with a gun.