听力原文： I am glad to see so many of you here. We've become really alarmed over at the health center by the number of students we are seeing, who are experiencing heating loss. First I want to go over some basics about hearing, then we can take a look at our school environment and see if we can figure out some ways to protect hearing. The leading cause of preventable heating loss is excessive noise. Too much moderate noise for a long time, or some types of intense noise for even a short time can damage hearing. Loudness is measured in units called decibels. One decibel is the lowest sound that the average person can hear. Sounds up to 80 decibels generally aren't harmful, that's noise like traffic on a busy street. But anything louder than 80 decibels, esp. with continuous exposure, may eventually hurt your hearing. Once you're up to around 140 decibels, that's like a jet plane taking off, then you might even feel pain in your ears. And pains are sure sign that your hearing is at risk. Even one exposure to a really loud noise at close range can cause hearing loss. So what you need to do is limit your exposure to harmful levels. If you pass along this hand-out, we can take a look at the decibel level of some common campus sounds. Notice how loud those horns are that people take to football games. They are really dangerous if blown fight behind you. Now, let' s try to generate a list of damaging noises.
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A. To plan ways to prevent hearing damage.
B. To inform. them about contagious ear infections.
C. To explain part of the physical exam entering students must have.
D. To provide background information for their course work.