Crossword

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Across
  1. 4. Main gas in earth's atmosphere
  2. 8. Tallest building in the world
  3. 9. Force that pulls object towards earth
  4. 10. Disaster happened in 2019
Down
  1. 1. Largest desert on the earth
  2. 2. Fundamental unit of heredity
  3. 3. First man-made satellite launched
  4. 5. Male cow called
  5. 6. Tallest type of grass
  6. 7. Discovered polonium and radium