Preposition Germ Warfare Chapter 1

Germ Warfare Chapter 1
_____ billions of years, the Earth has been our planet. We leaned how to live and thrive here and, with our huge numbers, we became the earth most successful life form. But durning the last few hundred years, we have faced a clever enemy: humans!
We are a type _____ bacteria. Bacteria are tiny living things that are so small, they can only be seen _____ a microscope. You may not be able to see us, but you are surrounded _____ millions of germs. We are everywhere around you- in the air, the water and the soil. In your body, bacteria help you to digest, or break down, the food you have eaten _____ the vitamins and minerals that you need to survive.
Most bacteria are helpful to other living things, such as plants and animals. _____ the soil, bacteria can break down dead animals and plants, turning them _____ the chemicals that plants need to live and grow. Humans have learned to use bacteria to make many useful things, such as yoghurt, cheese, septic tanks, medicines and chemical.
Most bacteria either help you or are harmless-but some of us are very dangerous bacteria that can cause disease and make humans very ill. These "bad"bacteria are the germ soldiers that we use _____ our battle to rule planet Earth!
For millions of years,humans have been fighting against us. But, _____ most of that time, we have been winning. We have special advantage. To humans, we are invisible! Who can fight an enemy they can't see?