Trees are one of the oldest plants on the earth. Just like us, trees change a lot 1 they grow. At one to three years old, young trees learn to 2 themselves. For example, many tree grow thorns (刺)to tell animals 3 near. Most young trees have large and deep green leaves to 4 enough sunlight and turn it into their food and energy. When trees are four years old, they are strong enough to 5 the challenge(挑战)in life. At the age of fifteen, they become young adults and grow more 6 . They will have their own flowers and fruit. After the trees are twenty to twenty-five years old, they are called real adults because they reach their 7 . Adults trees give us oxygen and natural beauty. If we 8 them very well, they will live healthily for many years. As time goes on, trees begin older and older and even 9 . At this time, they still have their important places in nature and uses for people. 10 many ways, the life of trees is like our own life experience. 小题1: A．before B．when C．after D．since 小题2: A．protect B．provide C．prevent D．pollute 小题3: A．to go B．to leave C．not to go D．not to leave 小题4: A．enjoy B．keep C．stay D．catch 小题5: A．get B．receive C．face D．welcome 小题6: A．fast B．faster C．slow D．slowly 小题7: A．weights B．heights C．styles D．sizes 小题8: A．look for B．look after C．look out D．look at 小题9: A．die B．hurt C．waste D．throw 小题10: A．On B．In C．For D．At