A、Face. B、Body. C、Arms. D、Feet. D短文一开始即点明了冻伤容易出现的部位，即手、脚、鼻子和耳朵，故答案为D)。

Frostbite is damage that happens when skin is exposed to extreme cold for too long.(16)It mainly happens on the hands, feet, nose and ears. People with minor cases of frostbite that affect only the skin may not suffer any permanent damage. But if deeper tissue is affected, a person is likely to feel pain every time the area gets cold. If blood vessels are damaged, people can suffer an infection.(17)Sometimes the only way doctors can treat an injury like this is to remove frostbitten areas like fingers and toes.
    To avoid cold-related injuries, here is a simple way to remember four basic steps to staying warm. Think of COLD—C. O. L. D. The C stands for cover. Wear a hat and scarf to keep heat from escaping through the head, neck and ears.(18)And wear mittens instead of gloves. In gloves, the fingers are separated, so the hands might not stay as warm as they would in mittens. The O stands for overexertion. Avoid activities that will make you sweaty. Wet clothes and cold weather are a dangerous combination. L is for layers. Wearing loose, lightweight clothes, one layer on top of another, is better than wearing a single heavy layer of clothing.(19)Make sure outerwear is made of material that is water-resistant and tightly knit. D is for dry. In other words, stay as dry as possible. Pay attention to the places where snow can enter clothing. These include the tops of boots, the necks of coats and the wrist areas of mittens or gloves.
16. In which part of the body does frostbite usually happen?
17. What do doctors sometimes have to do if the frostbitten area is hurt too badly?
18. Why are mittens better than gloves?
19. Which of the following is the best choice of an overcoat in the freezing weather?