(E) says, "Therefore, the Marcusian critique of advertising is mistaken except in its claim that advertisers exert economic power over those few people who are unable or unwilling to distinguish real from false needs."
The Marcusian critique makes the claim that most people aren't able to differentiate between real and false needs, not just a few people. (E) presents this as a claim from the Marcusians, but this could also be a claim that the author actually makes since she appears to make the implication that some people (uninformed, irrational ones) could potentially fall under the influence of advertising. However, with (E), it is presented as it came straight from the Marcusians, so this does not make sense.
(A) says, "Therefore, while in principle there might be grounds for holding that advertising is detrimental to society, the Marcusian critique does not provide such grounds."
The end of the passage concedes that advertising is potentially often misleading, but it also doubles down on the inadequacy and ultimate failure of the Marcusian view on how advertising harms people. In doing so, the author leaves open the possibility that advertising isn't honest while also refuting the Marcusian view. This is summarized nicely in (A), which is the best answer choice that would help logically complete the passage.
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