48. According to some analysts, whatever its merits, the proposal to tax away all capital gains on short-term investments would, if enacted, have a disastrous effect on Wall Street trading and employment.
(A) its merits, the proposal to tax
(B) its merits may be, the proposal of taxing
(C) its merits as a proposal, taxing
(D) the proposal’s merits, to tax
(E) the proposal’s merits are, taxing


Can you please explain why the answer is a and not b?

It looks like the decision is predicated on the difference in idiomatic usage between "proposal to tax..." and "proposal of taxing...". I think you'll agree that the former is better.

The usage of 'whatever' in this sentence is somewhat old-fashioned, but by no means incorrect. It's essentially equivalent to both words of 'regardless of' rolled up into one.

HTH. In any case, 1000SC problems are often not as clear-cut as the genuine article.