单选题：第二篇 Sprained (扭伤) Ankle　　One of the most common injuries te

第二篇 Sprained (扭伤) Ankle
　　One of the most common injuries teenagers and adults experience is a sprained ankle. A sprain occurs when the ligaments(韧带) of a joint are twisted(扭伤) and possibly torn. Ligaments are bands of fibers that hold the bones of a joint in position. A sprain can occur from a sudden twisting at the joint, or a stretching or tearing of the fibers of the ligaments. The injured area usually swells(肿胀) and becomes black and blue. Stepping off the sidewalk at the wrong angle or having one foot land in a hole while walking or running can leave you rolling on the ground in pain with an ankle on fire!
　　If you cannot walk without experiencing intense pain, you must seek medical help. If the pain is manageable, and you can walk, here are three words to help you remember how to treat yourself:
■ Elevate(抬高)
■ Cool
■ Bandage（打绷带）
　　As soon as there is injury to that ligament, there will be a certain amount of bleeding under the skin. Once the blood pools around the damaged blood vessels, swelling occurs. The pressure from the swelling results in additional stress and tenderness to the region. In order to reduce the degree of swelling, lie down as soon as possible and keep the ankle elevated so that it is actually higher than your heart. Next, to reduce blood distribution and keep bleeding(流血) to minimum, apply a cold pack. After 20 minutes, take the pack off, wait half an hour, and then reapply. This can be several times a day for a total of three days.
　　Never leave a cold pack on for more than 20 minutes at a time. Reducing the temperature in that area for an extended period of time signals the body to increase blood flow to raise the body temperature! Therefore, one accidentally triggers(引起) more blood distribution to the affected area by leaving a cold pack on for too long! Finally, bandage the angle. Be careful not to wind it too tightly; doing so can restrict blood flow and cause harm to the entire foot.
A sprain is caused by A．blood vessels being hurt in the foot
B．ligament fibers of a joint being twisted
C．constantly changing body temperature
D．elevating one’s ankle