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1: Active solar heating system 2: Soil 3: Community 4: Human 5: Water 6: Lead 7: Feeder 8: Environment 9: Range 10: Condition 11: Process 12: Carbon 13: Contamination 14: Current 15: Atom 16: Plant 17: Electricity 18: Conservation 19: Fishery 20: Animal (As of 07:39)