natural resources

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Across
  1. 3. dioxide constitutes up to 90% of Venus and mars
  2. 4. outermost layer of the earth
  3. 5. one of the expensive metal
  4. 6. core innermost layer of the earth
  5. 8. constitutes up to 78% of the earth
Down
  1. 1. constitutes up to 21% of the earth
  2. 2. helps in preventing soil erosion
  3. 4. hardest metal in the world
  4. 7. also found in urea and alkaloids