According to the theory of photo-periodism ______.A.birds should migrate in the middle of

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According to the theory of photo-periodism, ______.A.birds should migrate in the middle of the winterB.longer days cause changes in the bodies of birdsC.seasonal changes in the length of days do not affect migrationD.increasing daylight increases the distance of migration

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  • 正确答案:B
    B[注释] 本题解答依据在最后一句changes occur in the bodies of birds due to seasonalchanges in the length of daylight,即“日照时间的季节性变化会造成鸟类身体生理变化”,由此推断白天不论长还是短的变化都可能引起鸟类体内变化。故B.longer days cause changes in the bodies of birds正确。