글의 흐름으로 보아 아래 문장이 들어가기에 가장 적절한 곳은? One … | [법원직 9급 영어] 17년 1회차 기출문제 상세 페이지

글의 흐름으로 보아 아래 문장이 들어가기에 가장 적절한 곳은? 
One population of Berwick's swans wintering in England put on fat more rapidly than usual, making them ready to begin their Siberian migration early.

Wherever human light spills into the natural world, some aspect of life— breeding, feeding, migration—is affected. Some birds—blackbirds and nightingales, among others—sing at unnatural hours in the presence of artificial light. ( ① ) Scientists have determined that long artificial days—and artificially short nights—induce early breeding in a wide range of birds. ( ② ) And because a longer day allows for longer feeding, it can also affect migration schedules. ( ③ ) The problem with them is that migration, like most other aspects of bird behavior, is a precisely timed biological behavior. ( ④ ) Leaving early may mean arriving too soon for nesting conditions to be right.

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