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Why Do Leaves Change Color in Fall?
为什么秋天树叶会变色？
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In summer, leaves are green because of chlorophyll.夏天，叶子因叶绿素而呈绿色。
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Chlorophyll helps plants make food from sunlight.叶绿素帮助植物利用阳光制造养分。
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When days get shorter, trees stop making chlorophyll.白昼变短后，树木停止合成叶绿素。
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Other colors like yellow and orange were always there.黄色、橙色等其他颜色原本就存在。
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They were just hidden by the strong green color.只是被浓烈的绿色掩盖了。
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Some trees make red pigments when sugar stays in leaves.有些树木在糖分滞留于叶片时会生成红色色素。
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Cold, sunny days help bright red colors appear.寒冷晴朗的天气有助于鲜红色显现。
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Then wind or rain makes the leaves fall to the ground.随后，风或雨使树叶飘落至地面。