问题
单项选择题 A1/A2型题
在胸骨左缘第3、4肋间触及收缩期震颤，应考虑为（）
A.主动脉瓣关闭不全
B.室间隔缺损
C.二尖瓣狭窄
D.三尖瓣狭窄
E.肺动脉瓣狭窄
答案
参考答案：B
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在胸骨左缘第3、4肋间触及收缩期震颤，应考虑为（）
A.主动脉瓣关闭不全
B.室间隔缺损
C.二尖瓣狭窄
D.三尖瓣狭窄
E.肺动脉瓣狭窄
参考答案：B
Stop. Listen! What do you hear? You may hear many different sounds. Some of those sounds may be noise. Noise is a loud or unwanted sound. Noise can be caused by many kinds of machines, such as motorcycles, jet planes, farm tractors(拖拉机), rock music is also noise. What happens to people who live near noisy machines or use them over a period of time? Doctors have found that these people have trouble in sleeping. But, most important, constant(不断的) loud noise can cause a loss of hearing. Scientists use a unit of measure called decibel(分贝) to measure the loudness of a sound. The sound of a quiet room, for example, measures 35 decibels. Talking measures between 40 and 65 decibels. Sounds from traffic and from some rock bands can measure over 120 decibels. Noise at this high level(层次) causes the great hearing loss. 根据短文内容，选择正确的答案（每小题1分，共5分） 小题1:According to the passage, noise is .
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