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The world is full of creatures (生物), such as animals, plants and so on. But the smallest living creatures on the earth are bacteria. Actually, you can’t see them without a microscope. Bacteria may be small, but there are a lot of them around us!

Bacteria live on the earth for a long time. These bacteria can live everywhere. We can find bacteria in cold places, such as in deep Arctic ice and in hot places, such as the insides of bot spring.

We may only think bacteria can make us sick, but bacteria do many things to help life on earth live and grow. They help break down dead plants and animals into soil nutrients (土营养物).Without these nutrients, soil could not be used to grow food for humans and animals. Without bacteria, ecosystems would be less healthy because dead plants and animals would not break down properly.

▲ For example, they affect (影响) the taste of some types of bread. And without bacteria, we would not have cheese or yogurt.

The human body needs some bacteria to work properly. Microscopic bacteria help our stomachs work. Also, bacteria help clear dead skin cells. And some kinds of bacteria even fight off other harmful bacteria. Now, scientists use bacteria to make medicine to fight against illnesses. Bacteria just might be the most useful organisms on the earth!

1．According to the passage, which picture is bacteria?

A．

B．

C．

D．

2．Which of the following things can bacteria do in the passage?
a. make us sick.
b. break down dead plants and animals.
c. make ecosystems less healthy.
d. affect the taste of some food.
c. help us taste food.

A．abd

B．ade

C．bce

D．acd

3．What’s the structure of the passage?

A．①/②③④/⑤

B．①②/③④/⑤

C．①②/③④⑤

D．①/②③④⑤

4．What can be put in the blank “ ▲ ”?

A．Bacteria do well in making the ecosystem healthy.

B．Bacteria can make the bread taste better.

C．Bacteria are important in making cheese or yogurt.

D．Bacteria have something to do with the taste of some foods.

5．What is the writer’s purpose of writing the text?

A．To change people’s ideas about bacteria.	B．To introduce the creatures of the world.
C．To tell people the habits of bacteria.	D．To let people know the harm of bacteria.