Final answer:
The author uses logical reasoning and the credibility of NASA to inform readers about the benefits of neurofeedback in smart glasses, which corresponds with the rhetorical appeal to logos and establishes credibility. The correct option is D.
Step-by-step explanation:
The author of “NASA Brain training tech makes smart glasses” advances the purpose of the article predominantly through the use of logical reasoning and the credibility of NASA. The correct answer to the question is D. This approach aligns with the rhetorical appeal to logos, focusing on presenting factual information and logical arguments to inform readers about the benefits of using neurofeedback to increase focus. The mention of NASA adds to the credibility (ethos) of the technology being discussed, which may imply reliability and effectiveness without directly employing expert testimonials.