（1）     GWD-27-Q7

Providing initial evidence that airport 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 as much as that which is being emitted annually by all motor vehicles in the Chicago metropolitan area.

1. as much as that which is being emitted annually by all

2. as much annually as is emitted by the

3. as much compared to what is annually emitted by all

4. that emitted annually by all

5. that emitted annually compared to the

为什么答案是D？ 感觉TWICE WHAT 比较好。