Which of the following is an example of a biological system the Internet a biology textbook the heart lungs and blood vessels working together to carry oxygen throughout the body or a science fair project modeling the process of breathing in the human body

bacteria could be both, harmful and to us. harmful bacteria could make us sick and probably even by getting the chances of getting a disease, but good bacteria fight it off with your immune system. there is always bacteria everywhere we go. we need to make sure to wash our hands after using the restroom, before eating, after eating, after petting an animal too. so you see, bacteria is everywhere and is harmful or . i hope this . : ) : ) : )