新GRE小短文阅读练习题三十三
As the ozone layer in the Earth's upper atmosphere thins, it allows more ultra-violet radiation from space to pass through the upper atmosphere.Thus, since
the ozone layer recently started to thin over North America, the upcoming mea-
surement of ultraviolet radiation over North America should show that ultraviolet
radiation has increased in intensity at ground level there.
Which of the following, if true, most seriously weakens the argument given?
The ozone layer in the Earth's upper atmosphere has thinned to a much
greater extent over the Earth's southern pole than it has over North
America.
During the next decade, the countries of North America will completely halt
production of the chemicals that cause the ozone layer to thin.
Clouds absorb ultraviolet radiation, andcloud cover has been increasing
over North America in recent years because of changing weather patterns.
The instruments that are used to measure ultraviolet radiation near the Earth's
surface have not become significantly more accurate in recent years.
At any given time, ultraviolet radiation is typically more intense on mountain -
tops than at low-lying plains.
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