We know that trees are useful in our everyday life. They give us   1  things, such as wood, oxygen, rubber（橡胶）, medicines   2  many other things. They can also tell us a lot about our climate. The following are the reasons. If you cut   348  a tree, you can see that it has many rings. Most trees grow one new ring   4  year. Because of this, we know how old a tree is. A tree over a hundred   5  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   7  usually thin. When it is wet and warm, the rings
8  thicker. If the rings are suddenly very thin or suddenly very thick, it means that the 9  changed suddenly. If we look at the rings on the tree, we can learn about the climate in the past years. We can see
  10  changing today.
A．much               B．lot                 C．many        
A．so                 B．and                 C．while       
A．down               B．cross                   C．into        
A．every              B．many            C．some        
A．year old            B．old                 C．years old       
A．plants             B．rings                   C．leaves      
．A．is                B．are                 C．were        
A．are much               B．are more            C．is much     
A．day                B．year                C．climate     
A．how our climate is     B．how is our climate   C．how to our climate