to deliver messages to the brain to generate movement of muscles to provide a physical barrier to the body to produce carbohydrates for energy
I gave my students this multiple choice question: What is the primary function of skin cells?

Only one answer is correct among these 4 choices:
- to deliver messages to the brain
- to generate movement of muscles
- to provide a physical barrier to the body
- to produce carbohydrates for energy

Could you tell me which one is correct?

to provide a physical barrier to the body