Bunuel
Companies that have been successful in this age of globalization
have achieved that success both by selling to new, untapped markets and leveraging new, lower-cost sources of labor.
A. have achieved that success both by selling to new, untapped markets and leveraging
B. have achieved that success by both selling to new, untapped markets and by leveraging
C. have achieved that success both by selling to new, untapped markets and by leveraging
D. have been achieving that success both by selling to new, untapped markets and they leverage
E. are achieving that success by selling both to new, untapped markets and by leveraging
VERITAS PREP OFFICIAL SOLUTION:
This problem features the telltale signs of a parallelism error: the structure "both x and y..." with prepositions on either side of the word "both" in the answer choices should immediately signal to you that you can eliminate several choices by holding them up to the parallel structure test.
Here, choice A is not parallel: the first portion after "both" begins with the preposition "by" but the second omits that. Choice B does essentially the opposite: the second has the preposition "by" (after "and") but the first does not.
Choice D fails the parallel structure test ("by" is not parallel to "they"), as does E ("selling," the first verb, comes before "both," so it is therefore not parallel to "leveraging").
Therefore, choice C, which maintains parallel structure, is correct.