听力原文：W: Mr. Johnson, I burned my hand when I was cooking. What would you recommend? M: Try this medicine and also take a Vitamin C tablet every day. W: Vitamin C? For a burn? M: Yes, a cut or a burn, or even a broken leg, will not heal properly without Vitamin C. And, anyway, Mrs. Grant, you are a heavy smoker. W: Really? Why do smokers need Vitamin C? M: Cigarette smoking, even tension, can cause levels of Vitamin C in your body to go down. And since the human body doesn't produce Vitamin C, we have to get it from a Vitamin C supplement. Of course, there are plenty of reasons for you to stop smoking, but even nonsmokers need a proper amount of Vitamin C. (17)