In 1620, about half the USA was covered by forests. Today the forests have almost gone. A lot of good land has gone with them, leaving only sand. China doesn’t want to copy the USA’s example. We’re planting more and more trees. We’ve built the " Great Green Wall" of trees across northern part of our country.The Great Green Wall is 7,000 kilometres long, and between 400 and 1,700 kilometres wide. It will stop the wind from blowing the earth away. It will stop the sand from moving towards the rich farmland in the south. More "Great Green Walls" are needed. Trees must be grown all over the world. Great Green Walls will make the world better.
In 1620, about ______ the USA was covered by forests.[2分]
A lot of good land has gone with ______.[2分]
The Great Green Wall in China is ______ long.[2分]
Trees must be grown in ______.[2分]
______ will make the world better.[2分]