新prep2-206 分词在主系表结构中的问题

yaao

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.

A.which amounts to a little less than half the population of the state, down from nearly three-quarters only a decade ago

B.which amounts to a little less than half the population of the state, down from a decade ago, when it was nearly three-quarters

C.and that amounts to a little less than half the population of the state, down from a decade ago, when they were nearly three-quarters

D.amounting to a little less than half the population of the state, down from nearly three-quarters a decade ago(D)

E.amounting to a little less than half the population of the state, down from what it was a decade ago by nearly three-quarters

答案D

关于现在分词的解说中，分词短语不能在主系表结构中做伴随状语，大家帮忙看下D项在这个句子中做什么成份

OwenBBB

主系表结构中，句末的现在分词短语是作为主语或表语（两者一样）的定语修饰成分