Trees are one of the oldest" citizens（公民）" of our Earth． They keep our air clean ， reduce noise pollution， improve water quality and provide food and building materials．

    Just like us， trees change a lot as they grow． At I 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 tree 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 rapidly and become strong enough to face challenges later 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 tree is 20 to 25 years old that it becomes a real adult． The tree reaches its largest size． The adult tree gives us shade， oxygen and natural beauty； it is also a great place for a tree house， or a place for us to read a book， listen to music and so on． If we give the adult tree proper care， it will go on to live healthily for many years．

    Gradually， 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 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 the trees!

（1）What can it be used as when a tree becomes hollow？　　

A． A home to small animals．

B． Food for all animals．

C． Shade and beauty for people．

D． A place for a tree house．

（2）Put the following in the right order according to the passage．　　

①Grow very rapidly

②Become a real adult

③Have large， deep green leaves

④Grow older and die

⑤Produce flowers and fruit

A．②①③④⑤

B．③⑤①②④

C．①③⑤②④

D．③①⑤②④

（3）Why should we enjoy every minute of our own life according to the passage？　　

A． Because our life is becoming better and better．

B． Because tree give us so much and make our world beautiful．

C． Because the life of a tree is similar to our own life experience．

D． Because each period of life brings its own form of joy and challenge．

（4）The best title for the passage should be　　

A． The life of a tree

B． The kinds of trees

C． The mystery of a tree

D． The advantages of a tree

（5）Which of the following shows the structure（结构）of the passage？　　

（1＝ paragraph（段落）1     2＝ paragraph2， …）

A． 1→2，3，4→5，6

B． 1，2→3，4→5，6

C． 1→2，3，4，5→6

D． 1，2→3，4，5→6