Critical Reasoning (CR) | Inhabitants of the country Orctania suffer from a much lower incidence

Why D is the answer here.

D also explains why higher incidence of cancer in NON-Native peoples. In D, even if Native people don't know the combination, how would the non-native peoples know the combination. So non-native peoples would have all factors or improper combination of factors, this tells the reason for higher incidence in non-native peoples.

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