gwd的语法题

jiejiexi

Q18: GWD-13-30

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 there-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

amounting to a little less than half the population of the state, down from what it was a decade ago by nearly three-quarters
为什么a 不对？GWD7-Q40:

Since February, the Federal Reserve has raised its short-term interest rate target five times, and because of the economy’s continued strength, analysts have been predicting for weeks that the target will be raised again in November.

A.because of the economy’s continued strength, analysts have been predicting for weeks that the target will

B.with the economy’s strength continuing, analysts predicted for weeks that the target

C.because the economy continues strong, analysts predicted for weeks that the target would

D.due to the economy’s continued strength, analysts have been predicting for weeks that the target

due to the fact of the economy’s continued strength, analysts predicted for weeks that the target will
这题是有争议的，但是还是想问下。谢谢。 关于a与c的时态问题