We know that trees are useful in our everyday life. They1 us many things, such as wood, oxygen, rubber, medicines and many other things. They can2 tell us a lot about our climate(气候）. The following are reasons. If you3 a tree, you can see that it has many rings(年轮). Most trees grow one new ring4 year. Because of the reason, we know5 a tree is. A tree over a hundred years old means that it has more than a hundred6 When the climate is dry or very cold, the trees do not grow very much and their rings are usually 7 When it is wet and warm, the rings are much thicker. If the rings are suddenly very thin or suddenly very thick, this means that the 8changed suddenly. If we look at the rings on this tree, we can learn about the 9 for a hundred years. We can see10 our climate is changing today.
We all cry for water when we are thirsty. But do you know, in very hot, dry weather, plants also make very low sounds as if they are crying for help?
You see, in a plant's stem there are several hundred "water pipes" that bring water from soil all the way up to the leaves. When the ground turns dry, it becomes harder and harder for plants to do this.
On very hot days, plants have to get any water that they can get.
Scientist Robot Winter has found out that when plants can get no water, their "water pipes" snap(发出声音). When that happens, the whole plant vibrates(振动) a little.
Robot knows that healthy, well-watered plants are quiet. He also knows that dry plants are many insects' "favourite" and they often attack(袭击) them. How do the insects know which are healthy plants and which are not? Robot thinks that the insects may hear the plants "crying" and they may come to kill them.
I can't remember when I started collecting rubbish. It might be when I got tired of(厌倦) seeing rubbish in the forest near my home. I used to love going there to play with my dog. But one day there was so much rubbish there that I became very unhappy.
I decided I had to clean up the forest. I made my first trip to clean the forest that afternoon. I took a big black rubbish bag with me. Ten minutes after starting picking up rubbish, my bag was full! It had cans, bottles, broken glass and newspapers in it.
I go to the forest four times a year to pick up rubbish. I often stay there for three hours. After each trip, I look at all the rubbish. If any of it is recyclable, I will keep it. It makes me feel great to do something for the environment. I will keep picking up rubbish until people stop dropping it.
