Let us try to simplify the argument --

Exercise --> Better performance of physical organs such as the heart and the lungs

Brain = Physical organ

THEREFORE,
read the magazine (= Stimulus) that exercises your brain --> Improve your brain performance

As we read through, we figure that "brain" and "other physical organs" might not be comparable and that the argument is flawed.
Just because the brain is a "physical organ" we cannot infer that results similar to those found in heart and lungs will be applicable to the brain. Note that the initial argument is applicable only to some physical organs, not all. Moreover, the initial argument talks about physical exercise, not mental exercise. The argument makes the faulty assumption that because the brain is a "physical organ", similar results will be repeated.

Option A - Incorrect

"evidence that subscribing to the product being advertised has desirable consequences" -- No such evidence is offered. The only evidence offered is about improvement in physical performance.

Option B - Incorrect

"It ridicules people" -- no "ridicule" is made in the argument. "by suggesting that they do not believe that exercise will improve brain capacity" -- again no such suggestion is made

Option C - Incorrect

"process by which the product [= Stimulus] brings about the result [= increase in brain performance] claimed for its use" -- no such thing is done.

Option D - Incorrect

No careful analysis of "the concept of exercise" is performed.

Option E - Correct answer

"similar in another respect" = both are physical organs ---> "similar in one respect" = Exercise LEADS to improvement in performance of that organ.
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