Restaurant critic: Most people agree that the food at Marva’s Diner is exceptional, while the food at the more popular Traintrack Inn is fairly ordinary.
Conclusion
It should come as no surprise that Marva's food is great will Traintrack's food is ordinary.
Evidence
Traintrack's has a more convenient location than Marva's, and it by itself is almost enough to guarantee a steady flow of customers.
Evaluate
This is a super tricky conclusion to deal with, "the discrepancy should come as no surprise" is a mouthful. Much of the time, the conclusion on a Principle-Strengthen question would be something like "impermissible" / "should be avoided", and so we predict an answer that looks like such-and-such → impermissible
Here we'd be predicting something like such-and-such → discrepancy should come as no surprise
We might want to approach that conclusion with a more flexible mindset. What are some other ways to say "X should come as no surprise"? - X is what you'd expect - X frequently occurs - it's natural for X to occur
Because Traintrack's has a more convenient location than Marva's We would expect Traintrack's to have worse food than Marva's
or, equivalently
Because Marva's has a less convenient location than Traintrack's We would expect Marva's to have better food than Marva's
Goal
We need to pick an answer that establishes a clear connection between how convenient your location is (whether it guarantees customers) and how good your food is.
If we get a little gist-y and real world with this, our author is just saying,