十万个为什么·科学启蒙30篇（1）

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为什么树叶在秋天会变色？

In autumn, days get shorter and temperatures drop slowly.
Trees sense these changes and begin to prepare for winter rest.
Chlorophyll, the green pigment in leaves, breaks down as sunlight fades.
When green fades, yellow and orange pigments called carotenoids become visible.
Some trees also make red pigments called anthocyanins when sugars get trapped in leaves.
Soil moisture and weather conditions affect how bright the colors appear.
This color change helps trees conserve energy before shedding leaves.
Not all trees change color—evergreens keep their needles year-round.
Deciduous trees lose leaves to avoid water loss in cold, dry air.
Scientists study leaf chemistry to understand climate change effects on forests.

听 → 读 → 学表达 → 懂 → 今天会说这一句 → 跟读录音 → 自己说一句。

In autumn, days get shorter and temperatures drop slowly. 秋天，白昼变短，气温缓慢下降。
Not all trees change color—evergreens keep their needles year-round. 并非所有树木都会变色——常绿树全年保持针叶。
This color change helps trees conserve energy before shedding leaves. 这种变色有助于树木在落叶前节约能量。

这篇中文题目最接近哪一句？为什么树叶在秋天会变色？一次学校运动会的通知一份超市购物清单

课文第一句的意思更接近？秋天，白昼变短，气温缓慢下降。今天学校放假了。请把窗户打开。

这一课主要在讲什么？（看英文标题） Why Do Leaves Change Color in Autumn? How to cook noodles A maths worksheet

In autumn, days get shorter and temperatures drop slowly.

In autumn, days get shorter and temperatures drop slowly.

第一版：录下来、回听、再听标准音。系统打分以后再加。

用今天的表达，自己说一句。

例子：In autumn, days get shorter and temperatures drop slowly.