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苏十一UID：3950277

4. The passage suggests which of the following about air   pollution?A.     Further attempts to reduce emissions from
gasoline-fueled vehicles will not help lower urban
air-pollution levels.  
B. Attempts to reduce the pollutants that an individual  
gasoline-fueled vehicle emits have been largelyunsuccessful.
C. Few serious attempts have been made to reduce  
the amount of pollutants emitted by gasoline-fueledvehicles.  
D. Pollutants emitted by gasoline-fueled vehicles are  not the most critical source of urban air pollution.  
E. Reductions in pollutants emitted by individual
vehicles have been offset by increases in pollution
from sources other than gasoline-fueled vehicle
为什么选A？