1细节题
叶子的绿色来自什么？
第一关 · 短文精读
先通读一遍不查词，再回头点生词。
Level B1 · 约 135 词
Why Do Leaves Change Color?
In spring and summer, leaves are green. The green comes from a substance called chlorophyll. Chlorophyll helps the tree make food from sunlight, water and air.
In autumn, the days get shorter and the weather gets cooler. The tree stops making food, and the chlorophyll slowly breaks down. When the green disappears, other colors show up. They were in the leaves all along — we just could not see them.
Different trees turn different colors. Maple leaves usually become red, because they make a new red substance in autumn. Oak leaves often turn brown.
Some people think cold weather makes leaves change color. Cold helps, but the real trigger is shorter daylight. Even a warm autumn will bring the change, as long as the nights get longer.
带虚线的词可以点，点了显示中文。先通读一遍再点。
2推断题
秋天出现的黄、橙、红色，是从哪里来的？
3主旨题
根据作者的说法，真正触发树叶变色的是什么？
看解析
最后一段明确写道：Cold helps, but the real trigger is shorter daylight. 前三段讲的是过程，第四段才是结论——这类「结论放在最后」的结构，是小升初阅读题最常见的出题位置。