Explanation
Creating a filter: suppose that we dislike this original
sentence but can't easily find an objective error. In such a case, we can
proceed to (B) and search for objective defects, noting that we have not
decisively eliminated (A).
Finding objective defects: we might judge (B) less bad
than (A). We'll come back to it. The verb tenses in (C) are unnecessarily
involved -- in "was increasing" and "having become." So (C) is out. Choice (D)
has the same problems and also a parallelism error -- a missing "because" after
"as." Choice (E) also has a lack of parallelism between the phrase "because
of," which introduces a noun, and "because," which introduces a clause. Indeed,
that's also a problem with (A), between "because of" and the word "by." The
correct answer is (B).
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