Nguyên's crossword

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Across
  1. 5. What never goes up and only comes down?
  2. 7. What increases but never decreases?
  3. 8. What bird is known for being a symbol of peace?
  4. 9. I'm hollow, and if you touch me, I'll die. So who am I?
  5. 10. I have cities but no homes. I don't have any trees, only mountains. There is water here, but no fish. So what am I?
Down
  1. 1. Who works just one day a year and never loses his job?
  2. 2. What has legs yet is unable to move?
  3. 3. I have a hump on my back? What am I?
  4. 4. What invention enables you to see straight through a wall?
  5. 6. I have stripes and I'm related to a horse. What am I?