阅读下面短文，从各小题所给的四个选项中选出能回答所提问题的一个最佳答案.(10分)
Have you ever been ill？ When you are ill，you must be unhappy because your body becomes hot， and there are pains all over your body. You don’t want to work ,and you stay in bed, feeling very sad.
What makes us ill? It is germs(细菌). Germs are everywhere. They are very small and you can’t find them with your eyes,but you can see them with a microscope（显微镜）. They are very small and there could be hundreds of them on a very small thing.
Germs are always found in dirty water .When we look at dirty water under microscope，we shall see them in it. So your father and mother will not let you drink dirty water.
Germs are found in air and dust. If you cut your finger，then some of the dust from the floor go into the cut and some of the germs go into your finger. Your finger would become big and red，and you will have much pain in it. Sometimes the germs would go into your body，and you would have pain everywhere.
Which of the following is true？

A．If things are very small, they are germs.

B．If things can’t be seen，they must be germs.

C．Germs are only in dirty water.

D．Germs are everywhere around us.

What is a microscope used for?

A．Making very small things look much bigger.

B．Making very big things look much smaller.

C．Helping you read some newspapers.

D．Helping you if you can’t see things clearly.

Why don’t your parents let you drink dirty water?

A．Because you haven’t looked at it carefully.

B．Because water can’t be drunk.

C．Because there must be lots of germs in it.

D．Because water will make you ill.

Which of the following is not true？

A．Germs can be found both in water and in the air.

B．Germs can go into your finger if it is cut.

C．If your temperature is not OK，there must be germs in your body.

D．If your finger isn’t cut，there aren’t any germs in your body.

What’s the main idea of the passage？

A．Germs may make us ill.

B． Germs are in dirty water.

C．Don’t drink dirty water.

D．Take care of your fingers.