9．
In 1620，about half of the U．S．A．was covered by forests．In 1850，about a third was covered by forests．Today the forests have （5）A．almost gone．But too many trees are still being （6）E．cutdown in the U．S．A．There is only land．China doesn't want to （7）C．copy the U．S．A．'s example．So China has built a new Great Wall across the northern part of China．It is a"Great Green Wall"of trees．The Great Green Wall is 7000kilometres long，and between 400and 1700kilometres wide．The Great Green Wall will stop the wind from （8）D．blowing the earth away．It will stop the sand from moving towards the rich farmland．
| A．almost B．make C．copy D．blowing E．cut down |
8．
All living things need water．Fishes live in water．We need water to drink and use．Animals and plants need water，too．But now the water （1）pollution is very serious．We should try our best to make the water clean．
There are two kinds of water---sea water and fresh water．Sea water is （2）salty and we can't drink it．We drink fresh water．
Water is an interesting thing．When we boil water，it will （3）turninto steam．If we put a piece of glass over the steam，it will cool down and turn back into water drops．If we put some water into a fridge，it will （4）freeze and change into ice．
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| A．turn into B．place C．pollution D．freeze E．salty |
There are two kinds of water---sea water and fresh water．Sea water is （2）salty and we can't drink it．We drink fresh water．
Water is an interesting thing．When we boil water，it will （3）turninto steam．If we put a piece of glass over the steam，it will cool down and turn back into water drops．If we put some water into a fridge，it will （4）freeze and change into ice．