CROSSWORD 7 PLUS

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Across
  1. 1. between cattle and goats on pasture
  2. 6. synthetic insecticide
  3. 7. substances that cause pollution
  4. 9. between lice and head hairs
  5. 10. between sharks and remora
  6. 13. of mosquitoes and lizards
Down
  1. 1. between host plant and orchid
  2. 2. cutting down forests
  3. 3. the covering of the water surface by algae
  4. 4. relationship between bean roots and Rhizobium bacteria
  5. 5. produced from refrigeration equipment
  6. 8. chemical element with the symbol Pb
  7. 11. a gas that can cause global warming from manure
  8. 12. gas produced from animal faeces mixed with vegetable waste