完形填空。
Dear human beings,
Hi! I'm 80 years old now. So I've seen 1 of the world. We've lived on Earth with you thousands of years. Each day we release(释放) O2 and remove harmful gas so that you have fresh 2; we help prevent the Earth's soil（土壤）from being washed away, and above all, we give all kinds of fruits, nuts, beans as well as 3 to you.
We are now in great 4 because of you. You are killing us at a terrible speed. You are burning and cutting down millions of us each year, but you're not 5enough. For every tree being planted today, 30 trees are being cut down. What would you do if all of us 6? Perhaps you would die, too.7 us, you wouldn't get enough material for buildings, furniture（家具）, paper products, and your cities would 8ugly. Moreover, air pollution and noise pollution would become more and more serious, and your life would become nasty.
The 9 thing for you to do now is to stop your bad manner. We are the best fighters 10 pollution and we are your best friends!
Your friend,
An old tree
