科普说明篇
滚动组合训练（一）
(时间：30分钟)
Ⅰ.完形填空。
Trees in the Amazon rainforest(雨林)are showing scientists the past so the scientists can learn what will happen in the future.
Have you 1 tree rings?Some trees create rings every year 2 they grow. These rings can be 3 in tree trunks(树干)when the trees are cut down. A tree’s 4 can tell us how old the tree is, but UK scientists have 5 a way of learning about the climate of the rainforest in the past from the tree rings.
