[单选题]
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Deduce why is there a downward trend in the area of the ozone hole in recent years.
A. Errors due to measurements taken in recent years
B. An international agreement in the 1980s to eliminate the use of ozone-depleting substances (ODS)
C. An increase in the use of CFCs and methyl bromide
D. A decrease in tropospheric ozone
参考答案:
B
本题详细解析:
The Montreal Protocol was successful in reducing the size of the ozone hole. It is an international agreement that was signed in 1987 and was designed to protect the ozone layer by phasing out ozone-depleting substances (ODS),
The measurements taken are done by satellites and are taken daily to eliminate errors (Option A).
The manufacture of CFCs has been phased out and the use of methyl bromide has decreased. Both CFCs and methyl bromide contributed to the formation of the ozone hole over time (Option C). These chemicals persist in the atmosphere and slowly move from the troposphere to the stratosphere, where they have detrimental effects.
Tropospheric ozone causes breathing problems and asthma, is found much closer to the ground, and is formed from fossil fuel emissions and UV radiation. It does not affect the stratospheric ozone (Option D) in which the ozone hole is found.
