B. Protein
Amino acids are organic compounds that combine to form proteins. Amino acids and proteins are the building blocks of life. When proteins are digested or broken down, amino acids are left. The human body uses amino acids to make proteins to help the body: Break down food.
Im not 100 percent sure, but I believe that the answer is D) because A), B), and C) are all equally necessary. Yet D) seems to have a much higher level of importance
On because of the suns heat. So, it would be on to protect it from sunburn.
