Trees are useful to man in three important ways.

The first important way is that they provide man with wood and other products. Trees provide not only man with food, but also many animals with food. Without trees, many animals could not live on earth. It’s not easy for man to live on earth, either.

The second important way is that trees give us shade（阴凉）. On a hot summer day, people are eager（渴望）to have a rest under the tree after they have a long walk. You can imagine how important the shade of a tree is to man and animals.

The third important way is that trees help to prevent droughts and floods（防止干旱和洪水）. However, in many parts of the world, man hasn’t realized the third way. They cut trees down in large numbers. In the end, they find that they have lost the best friends they had.

3 . Mr. Guo is a teacher from Xi’an. He asked his students to hand in their homework through a QRcode (二维码). “We spent an hour or two in class learning how to generate (使产生) the codes, and in the end everything gets easier,” said Guo. “When students finish the homework, they keep it on WeChat. Then, each student makes his own QR code and gives it to me. So I can check their homework everywhere using my computer or telephone.”

The QR codes can be sent to Mr Guo by email, QQ and WeChat When Guo scans (扫描) his students’ QR codes, their homework appears on his phone. He finds that their homework becomes more creative, with many pictures, music and even videos.

Guo’s students like the new way and think it is interesting. “We are living in the information age. Many students like to work with computers, which makes learning more fun.” said Tingting, a student of Guo’s.

“The paper is not easy to keep, but the code is easy to keep and share.” Guo said, “It is worth trying to use new technology in education. Education itself is a kind of creation. I don’t want my students to fall behind the times.”

However, some parents are worried. They are afraid that their children will spend too much time on computers and less time communicating with teachers. But in fact, it’s unnecessary. Students still need to look up information in books and write it down when they do their homework. They only use the code when they hand in their homework, which doesn’t take them too much time. Also for teachers it allows them to check the students’ homework at any time. And it’s also an easy way to share homework with other students.