8. The widely accepted big bang theory holds that the
universe began in an explosive instant ten to twenty
billion years ago and has been expanding ever since.
(A) that the universe began in an explosive instant
ten to twenty billion years ago and has been
expanding
(B) that the universe had begun in an explosive
instant ten to twenty billion years ago and had
been expanding
(C) that the beginning of the universe was an
explosive instant ten to twenty billion years ago
that has expanded
(D) the beginning of the universe to have been an
explosive instant ten to twenty billion years ago
that is expanding
(E) the universe to have begun in an explosive
instant ten to twenty billion years ago and has
been expanding

OA A

GMAT's explanation for why choice E is wrong:
E) The verb phrases to have begun and has been
expanding both reference the same subject of
the clause, universe, and therefore need to be
parallel.

What does parallel mean hear? I realize that it is unnecessary to have past perfect tense, but I did not understand why they are not in parallel. Please explain.