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  3. Ground-level ozone is an air pollutant that causes human health problems even at very low levels. It also damages crops and othe

Ground-level ozone is an air pollutant that causes human health problems even at very low levels. It also damages crops and othe

admin2014-01-13  28
问题     Ground-level ozone is an air pollutant that causes human health problems even at very low levels. It also damages crops and other vegetation. It is a key ingredient of urban smog. "Good ozone" occurs naturally in the stratosphere approximately 10 to 30 miles above the earth’s surface and forms a layer that protects life on earth from the sun’s harmful rays.
    "Bad ozone" is formed in the earth’s lower atmosphere, near ground level, when pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants, and other sources react chemically in the present of sunlight. Ozone pollution is a concern during the summer months when the weather conditions needed to form ground-level ozone — lots of sun, hot temperatures — normally occur. The length of ozone season varies from one area of the United States to another. Southern and southwestern states may have an ozone season that lasts nearly the entire year.
    Ozone can irritate lung airways and cause inflammation much like sunburn. Other symptoms include wheezing, coughing, pain when taking it deep breath, and breathing difficulties during exercise of outdoor activities. People with respiratory problems are most vulnerable, but even healthy people who are active outdoors can be affected when ozone levels are high. Repeated exposure to ozone pollution for several months may cause permanent lung damage. Anyone who spends time outdoors in the summer is at risk, particularly children and other people who are active outdoors. Even at very low levels, ground-level ozone triggers a variety of problems including aggravated asthma, reduced lung capacity, and increased susceptibility to respiratory illnesses like pneumonia and bronchitis.
    Ozone damage can occur without any noticeable signs. People who love in areas where ozone levels are frequently high may find that their initial symptoms go away overt time — particularly when exposure to high ozone levels continues for several days. Ozone continues to cause lung damage even when the symptoms have disappeared.
What does the word "vulnerable"(Line 3, Para. 3)most probably mean?
选项 A、Hard to deal with.
B、Harmful and dangerous.
C、Easy to be hurt or affected.
D、Hot in temper and hard to calm down.
答案C
解析 词义推断题。第三段提及长期参加户外运动的健康人在臭氧水平高时，也很容易受到影响(affected)，而有呼吸病的人就更vulnerable，两者是递进的关系。从下文中的affected可知，vulnerable“有受影响”的意思。故答案为C。
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