大家帮忙看一下这里的that指代什么，以及原因

许楚iris

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.

A.    as much as that which is being emitted annually by all
B.    as much annually as is emitted by the
C.    as much compared to what is annually emitted by all
D.    that emitted annually by all
E.    that emitted annually compared to the

that记得是核心词指代，那么它应该指代的是amount，可是D选项中，emitted应该是做定语修饰污染物啊，能直接修饰amount吗？还是说这里that指代的是the total amount of pollution，可是如果这样的话that就没有核心词指代啊……

HarrisZheng

指代整个名词短语

HarrisZheng

其实要看句意，如果后面的比较对象不是污染物，就用that of sth else

许楚iris

其实要看句意，如果后面的比较对象不是污染物，就用that of sth else

-- by 会员 HarrisZheng (2011/12/8 2:14:01)

that不是核心词指代吗？20 percent of adults，核心词是20 percent，这道题为什么就必须要带着后面的pollution呢？

sisichen666

指代的是the total amount of pollutant