When you have a cold, you must be unhappy   because your body becomes hot, and there are pains   all over. You don't want to work, you stay in bed, feeling terrible. What makes you ill? It's _ . Germs are everywhere. They are very small and you can't find them with your eyes but you can see them with a microscope  . They are very small and there could be hundreds of them in or on a very small thing. Germs are always found in dirty water. When you look at dirty water under the microscope, you can see them in it. Germs are found not only in water. They are also found in air and dust  . If you cut your finger  , and if some of the dust goes into the finger, it will become big and red, and you will have much pain in it. Sometimes germs will go into your body and you will have pain everywhere. The writer  talks about  _  .
how to keep dirty water clean how to look after your fingers how to find germs in the dirty water what can make you ill