Research Comparing Rates of Seasonal Affective Disorder (SAD)in Canada and Iceland

Research comparing rates of seasonal affective disorder (SAD) in Canada and Iceland has demonstrated that

A) all populations living at high latitudes are equally likely to experience SAD.
B) more Canadians experience SAD than Icelanders,suggesting that Icelanders may have developed some genetic protections against SAD.
C) more Icelanders experience SAD than Canadians,suggesting that Canadians may have developed some genetic protections against SAD.
D) native Icelanders or Canadians were unlikely to experience SAD,but people who immigrate to those countries are extremely vulnerable to SAD.