Crossword puzzle

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Across
  1. 2. a strong effect
  2. 3. a hundred years
  3. 6. an advanced state of human society
  4. 8. to make it better
  5. 9. used a variety of plants for food
Down
  1. 1. an bridge of ice
  2. 4. before the birth of christ
  3. 5. all living things and non-living things together
  4. 7. to become advanced