任务型阅读: 先通读下面的短文，然后根据短文内容和表格，在空格内填入一个适当         的单词，使意思完整.（共5分）
Trees are one of the oldest citizens (公民) of our earth. Just like us, trees change a lot as when they grow. At 1to 3 years old, young trees learn how to protect themselves. For example, many trees grow thorns(刺) to tell animals not to go near. Most young trees have large, deep green leaves so that they can catch enough sunlight and change it into their food and energy.
When trees are 4 years old, they begin to grow very fast and become strong enough to face challenges in life. At the age of 15, trees become young adults. They grow more slowly and begin to produce flowers and fruit.  It is not until the trees are 20 to 25 years old that they become real adults. The trees reach their largest sizes. Adult trees give us many things such as oxygen(氧气) and natural beauty.  If we give them good care, they will go on to live healthily for many years. In many ways, the life of trees is like our own life experience. So, enjoy every minute of the life of the trees because they are very helpful to the environment.

Title: The      of trees
	Growing	Things they can do
1 to 3 years old	Growing thorns to tell animals to       away from them.	Learn to protect themselves； Catch sunlight and change it into food and energy.
4 years old	Becoming strong enough	Face challenges
15 years old	Becoming young adults	Produce flowers and fruit
20 to 25 years old	Becoming real adults； Reaching their largest sizes	Give people many things       oxygen(氧气) and natural beauty. They can be of great      to our environment.