ANSWER CA. it is not only the price that is offered while entering the market, but also at what speed goods are rolled out in the market that determines the success of a marketing campaign.
INCORRECT : "it is" before not only not necessary + faulty parallelism structure between the phrase after not only and but also.
+ at what speed (little awkward)
B. it is not only the price that is offered while entering the market, but also the speed at which goods are rolled out in the market, determines the success of a marketing campaign.
INCORRECT : "it is" before not only not necessary + the presence of "it is" makes that a "that" is missing before determines.
C. not only the price that is offered while entering the market, but also the speed at which goods are rolled out in the market determines the success of a marketing campaign.
Seems legit to me.
D. what determines the success of a marketing campaign is not only the price that is offered while entering the market, but also how fast goods are rolled out in the market.
WEIRD SENTENCE STRUCTURE + I would better stick to speed rather than "how fast".
E. the success of a marketing campaign is determined not only by the price that is offered while entering the market, but also how fast goods are rolled out in the market.
INCORRECT faulty of parallelism we should have after but also "by..."
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