3. cell wall
The cell wall is a rigid supporting structure.
If all humans had the same DNA, and one person got the cold, everyone would die at some point. The more diversity there is the more chance of surviving an outbreak or natural disaster or something. Think of the flu. there are HUNDREDS of strains out there. some are resistant to our medicines and others aren't.
I think it’s insulin becaus Without insulin, glucose may be present in the blood but the cells are unable to utilize it. People with diabetes lack an adequate supply of insulin
I could help if I knew what you needed help with