North Carolina Cosmetic Arts Practice Exam

The skin is considered the first line of defense against disease because it acts as a protective barrier against pathogens and other foreign invaders. Option A is not the best choice because while the skin is one of the largest organs of the body, it is not necessarily the second-largest and this information is not relevant to the question. Option C is incorrect because the skin also plays important roles in regulating body temperature, retaining moisture, and producing vitamin D. Option D is incorrect because the skin is an essential part of the body's thermoregulation system, helping to regulate internal body temperature by dilating or constricting blood vessels and controlling sweat production. Therefore, option B is the most appropriate answer.