(A) “Buyers are more likely to choose higher functionality over better aesthetics” — not necessarily supported; the principle given is about balance, not functionality preference.
(B) “Creating a model that equally balances aesthetics and functionality helped Glide take the lead of the skateboard industry” — extreme: we don’t know Glide took the “lead” of the whole industry, only that it sold more than Slide’s latest model.
(C) “Slide changed its strategy by only a small amount” — no information about the magnitude of change.
(D) “Glide’s latest product’s aesthetic and functional levels were closer to each other than those of Slide’s latest product” — Yes, this directly matches the inference from Step 2.
(E) “Glide increased its emphasis on aesthetics for its latest model” — plausible, but not necessarily true; maybe Slide increased functionality a lot but still had a bigger gap. But the given facts only require Glide’s model to be more balanced, not specifically that Glide increased aesthetics.
The most strongly supported is (D) — it restates the necessary condition for Glide’s higher sales given the balance–sales relationship.