语法题，求解啊~~~

tbuslf

for the first time in the modern era, non-Hispanic Whites are officially a minority in California,which amounts to a little less than half the population of the state,down from nearly three-quarters only a decade ago.
正确答案为amounting to a little less than half the population of the state,down from nearly three-quarters a decade ago.
我想问下A为什么不对？这里为什么可以直接加amounting to ?
大谢了各位！

Gail小M

which 不能指代前一句话
一般用V-ing或者新名词代替which的表达...