(单词翻译:单击)
听力文本
Smog is up 65 percent in the western U.S., according to a new study.
根据一项新的研究，美国西部烟雾污染上升百分之65。
Researchers say it's because of Asian countries' emission levels of nitrogen oxides, which have tripled since 1990.
研究人员表示，这是因为亚洲国家的氮氧化物排放水平，自1990以来增加了三倍。
The findings come from pollution data collected in cities and national parks across the western U.S.
这些发现来自美国西部城市和国家公园收集的污染数据。
The Asian-made gases travel across the ocean. They've offset the 50 percent cut in emissions of nitrogen oxides made by the U.S. over the past 25 years.
亚洲排放的气体穿越海洋。它们抵消了过去25年美国氮氧化物排放量削减百分之50。
Researchers say a global strategy is necessary in order for the U.S. to meet air quality objectives.
研究人员表示，有必要采取全球战略满足美国的空气质量目标。
High levels of these nitrogen oxides can be harmful to people and animals.
高浓度的这些氮氧化物可能对人和动物有害。
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词汇解析
1、national
国家的;全国的
Ruling parties have lost ground in national and local elections.
执政党在全国和地区选举中均败北。
major national and international issues.
国内和国际重大问题
国民的;民族的
the national characteristics and history of the country.
这个国家的民族特征和历史
Baseball is the national pastime.
棒球是全民性的休闲运动。
国民;国人
a Sri-Lankan-born British national.
出生于斯里兰卡的英国国民
2、necessary
必要的;必需的
I kept the engine running because it might be necessary to leave fast.
我没让发动机熄火，因为也许需要迅速离开。
We will do whatever is necessary to stop them.
我们要采取一切必要措施去阻止他们。
(结果或联系)必然的，势必的
Wastage was no doubt a necessary consequence of war.
巨大的损耗无疑是战争的必然结果。
Scientific work is differentiated from art by its necessary connection with the idea of progress.
科学工作与艺术的区别在于它与人类进步有着必然联系。
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