阅读理解。

     Trees are one of the oldest "citizens (公民)" of our Earth. They keep our air clean, reduce noise pollution,

improve water quality (质量) and provide food and building materials.

     Just like us, trees change a lot as they grow. At l to 3 years old, young trees learn how to protect

themselves. For example, many trees grow thorns (刺) to warn 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.

     当小树成长到四岁的时候，它们成长开始加速并且变得足够强壮以面对未来生命中的挑战。  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 tree is 20 to 25 years old that it becomes a real adult. The tree reaches its largest size. Not

only does the adult tree give us shade, oxygen (氧气) and natural beauty; it is also a great place for a tree

house, or a place for us to nap, read a book, listen to music or sip.(小口喝) tea. If we give the adult tree

proper care, it will continue to live healthily for many years.

     Gradually (渐渐地), trees begin to grow older and older and even die. At this time, they still have their

important place in nature. When a tree becomes hollow (空心的) or part of it becomes dead, it provides a

home to small animals' and is a source of food for many other animals.

    In many ways, the life of a tree is similar (相似的) to our own life experience. When we are looking at the

life of a tree, we learn about that each period of life brings its own form of joy and challenge. Enjoy every

minute of the life of the trees and take care of the trees!

1. How do young trees protect themselves? And why do they have large, deep green leaves?

    ___________________________________________________________________

2. Why should we enjoy every minute of our own life?

    ___________________________________________________________________

3. 将文中画线的汉语句子翻译成英语。（一空一词）

   When trees are 4 years old, they begin to grow very rapidly and become ______ ______  to face

    challenges later in life.

4. 将文中画线的英语句子翻译成汉语。

     ___________________________________________________________________

5. 根据短文内容，写出能概括全文大意的句子。 

     ___________________________________________________________________