问题详情

Text 4
Nobody can be really free from the sound. Whether we live in the middle of a modern city or a faraway village, we are surrounded by sound every day such as the sounds from television and radio, household appliances, and traffic. Sound makes up a part of our life.
In fact, most of us can not bear total silence. Sound gives us a sense of safety and brings us joy. Scientific tests have also proved that total silence is a very frightening experience for human beings. A recent report shows that people feel quite lonely without background sound while they are working. The background sound which doesn"t change too much may even help people to concentrate.
However, sometimes, sound is not helpful and joyful in people"s life. Normally, we hear these sounds at safe levels that do not affect our hearing. However, when we are exposed to harmful noise-the sounds that are too loud or loud sounds that last a long time, sensitive structures in our inner ear can be damaged, causing hearing loss.
Besides, unpleasant sounds, particularly sudden and uneven ones, may cause fear and anger. Noise is a source of stress, which can lead to tiredness, irritability and headaches. Noise can also raise blood pressure, putting strain on the heart. People living in homes exposed to high levels of road-traffic noise were more likely to report having hypertension, according to a study in Environ-mental Health. The researchers estimate the noise levels for the addresses of more than 24,000 Swedish. They found that people exposed to an average traffic-noise level above 64 decibels
(slightly louder than a normal conversation) were 52% more likely than people exposed to 45 decibels of road noise to report having high blood pressure, a key risk factor for heart disease, after removing age, socioeconomic status, and other variables. Noise exposure could cause hypertension by persistently elevating the body"s level of stress hormones.
Now we know that noise is harmful to our health, but can we get used to the excessive noise？ The answer is NO. If, after long exposure to excessive noise, we stop hearing it - because we have become deaf !
56. From the first and second paragraphs we learn that___________
[A] sound is requisite in our life.
[B] total silence does not really exist.
[ C] the background sound will distract our attention.
[D] people had better work in an environment without any sound.请帮忙给出正确答案和分析，谢谢！