다음 글 바로 앞에 올 내용으로 가장 적절한 것은?

[2점]

But if this is so, how can we explain accounts from Arctic and Antarctic explorers who, in spite of exposure to very cold conditions, did not catch cold? Then, upon returning to the warmth and comforts of civilization, they caught colds immediately. Another evidence may be found in the experiences of prisoners of World War Ⅱ Nazi camps. During the late autumn and winter months, prisoners were forced to take showers and then stand wet and naked in the open air. They fully expected to catch colds; to their surprise, most did not.

① 감기의 원인은 다양하다.

② 포로들이 감기에 잘 걸린다.

③ 추위가 감기의 주요 원인이다.

④ 감기는 각종 질병의 원인이 된다.

⑤ 극지방에는 감기 바이러스가 없다.