Why don't natural killer cells destroy normal body cells?

Now it's your turn to investigate human impact around the world. grab your virtual lab coat and put on your environmental science hat. you will be taking a trip around the globe to explore three locations. at each location, you will investigate the cause and effect relationships of deforestation, desertification, and urbanization. you will also gather evidence of how these factors have impacted the environment over time

Which chemical equation is unbalanced? which chemical equation is unbalanced

Can someone give me the answers to this?