完形填空。
We know that trees are useful in our everyday life.  They __1__ us many things, such as wood, oxygen,
rubber, medicines and many other things.  They can __2__ tell us a lot about our climate. The following
are the reasons.  If'you, __3__ a tree, you can see that it has many rings (年轮).  Most trees grow one
new ring __4__ year. Because of this reason, we know __5__ a tree is.  A tree over a hundred years old
means that it has more than a hundred __6__ . When the climate is dry or very cold, the trees do not
grow very much and their rings are usually __7__ .  When it is wet and warm, the rings are much
thicker.  If the rings are suddenly very thin or suddenly very thick, this means that the__8__ changed
suddenly. If we Iook at the rings on this tree, we can learn about the __9__ for a hundred years. We can
see__10__ 0ur climate is changing today.
(     ) 1. A. tell
(     ) 2. A. not
(     ) 3. A. cut down
(     ) 4. A. many
(     ) 5. A. how big
(     ) 6. A. trees
(     ) 7. A. big
(     ) 8. A. climate
(     ) 9. A. people
(     ) 10. A. how

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