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
(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