GWD6-Q18 求教

wooky

原题目是：

In California today, Hispanicsunder the age of eighteen account for more than 43 percent, compared with adecade ago, when it was about 35 percent.

A. In California today,Hispanics under the age of eighteen account for more than 43 percent, comparedwith a decade ago, when it was about35 percent.
B. Ofthe Californians under the age of eighteen, today more than 43 percent of themare Hispanic, compared with a decade ago, when it was about35 percent.
C. Today, more than 43percent of Californians under the age of eighteen are Hispanic, compared withabout 35 percent a decade ago.
D. Today,compared to a decade ago, Californians who are Hispanics under the age ofeighteen account for more than 43 percent, whereas it wasabout 35 percent.
E. Today,Hispanics under the age of eighteen in Californiaaccount for more than 43 percent, unlike a decade ago, when it wasabout 35 percent.
答案选C， 我也是选的C， 只是解释那里说A B D E 都是 it 指代不清，小弟一直没搞懂，这些 it 在这里到底可以指代什么？为什么指代不清了？ 希望大神们帮个忙

wooky

没有人吗？