【正确答案】 B

【答案解析】[听力原文] No organ of the body is less appreciated than the skin, one of our biggest organs--and the most important telltale--it mirrors the state of our health, our age, and our race. Occupation and way of life may also become indelibly imprinted for all to see. Here are some facts about our outer covering organ to show that there is more to the skin than meets the eye. Your skin is your body’s thermostat. It adjusts heat gain and loss so that the internal temperature remains within the normal range of 97 to 99 degrees. It takes about two square yards of skin to cover the average adult from head to toe. Undoubtedly the most intricate wrapping in existence, the skin contains 3 million cells, three feet of blood vessels, and twelve feet of nerves in each area the size of a postage stamp. The widest difference between the darkest human skin and that of an albino is brought about by not more than 1/25 of an ounce of melanin. As far as is known, the amount of this dark brown or black pigment accounts for our variations in racial colors, including yellow, brown, and black.