题目选项分析

Providing initial evidence that airports are a larger source of pollution than they were once believed to be, environmentalists in Chicago report that the total amount of pollutant emitted annually by vehicles at O'Hare International Airport is twice that emitted annually by all motor vehicles in the Chicago metropolitan area.

Providing initial evidence that airports are a larger source of pollution than they were once believed to be, environmentalists in Chicago report that the total amount of pollutant emitted annually by vehicles at O'Hare International Airport is twice that emitted annually compared to the motor vehicles in the Chicago metropolitan area.