GMAT Sentence Correction (SC) | Re: Of all the vast tides of migration that have swept through

Of all the vast tides of migration that have swept
through history,maybe none is more concentrated as
the wave that brought 12 million immigrants onto
American shores in little more than three decades.
(A) maybe none is more concentrated as
(B) it may be that none is more concentrated as
(C) perhaps it is none that is more concentrated
than
(D) maybe it is none that was more concentrated
than
(E) perhaps none was more concentrated than

What is wrong with choice (d)? thx!