A tree can go hungry when it needs food to grow and it likes sugar very much. It's not (A) ____ same sugar in candies, but a special kind called glucose (葡萄糖) that makes trees grow. Trees make their sugar in their leaves. The sugar in the leaves then is spread into all other parts of the tree. This kind of sugar is made in a process (B) called photosynthesis (光合 作用).
Photosynthesis happens when a tree needs the sunlight and chlorophyll (叶绿素) to (C) turn CO2 and water into glucose. This glucose is the food that a tree needs when it grows. When the leaves are turning green, we know the tree is eating. But it isn't the glucose that makes the leaves green. It is the chlorophyll.
In spring and summer, trees grow the most ( D) 因为它们能吸收足够的阳光. Days become shorter and there is (E) ____ sunlight when autumn comes. This makes a tree realize it's time to get ready for winter. The leaves begin to turn red, orange and golden because there is less sunlight and water for photosynthesis, (F) and the green chlorophyll is going to disappear. As winter is coming, the tree has enough food it has kept when it is still warm and passes the season in a resting state, just like bears do! The only difference between them is that bears get into a cave and lie down to rest while trees lose their leaves and stand up to fall asleep.
