We can see walls everywhere in the world. But the Great Wall of China is __1__ of all. The Chinese call it“The Ten-Thousand-Li Great Wall.”It is, in fact（事实上）, more than 6,000 kilometres long. It is 6-7 metres __2__ and 4-5 metres wide from side to side. In most places, five horses or ten men can walk side __3__ side along the top.

　　When you visit the Great Wall, you can't help wondering（渴望知道）how the Chinese people __4__ build such a great wall __5__ years __6__ __7__ any modern machines, it was really difficult to built it. They had to do all the work by hand. It took millions of（几百万）men hundreds of years to build it.

　　The Great Wall has a history of over two __8__ years. The men began to build the first part of it about 2,700 years ago. Qin Shihuang __9__ all the walls up. He thought that could keep the enemy（敌人）out of the country.

Forests help to keep water from running away，so drought（干旱）doesn’t often happen．Chinese people have built a“Great Wall”of trees，millions of trees across the northern part of the country．

    The Great Green Wall 1 ________ （be）7,000 kilometres long，and it will stop the wind from 2 ________（blow）the earth away．It 3 ________already ________（save）a lot of land．

    Wang Feng is a worker at Yulin in Shanxi Province．He 4 ________ （work）on the Great Green Wall with many other people．We 5 ________ （visit）him at his workplace and when we saw him he 6 ________ （work）among the trees．He told us something about his work“We must 7 ________ （plant）many thousands of trees every year，”he said“You see all those small trees over there on that hill? That was sand five years ago．Now it's a young forest! In a few years’ time，we 8 ________（cover）those mountains with trees，too!”He pointed to the high mountains far away．

    Was it difficult 9 ________ （work）on the Great Green Wall?

    Yes，It’s hard work．but it's very important．The only problem is we have to 10 ________（grow）our own food．But thanks to the Great Green Wall，the land produces more crops．So the more trees there are，the better harvest we have．”