I think he just means that the structure is [info presenting one option] + [conclusion picking the other option without explanation] but in D the left side was considered in the premise and conclusion in a reasonable way ie didn't unwarrantedly eliminate a possibility. I think you can eliminate answers based on the conclusion but your thought process should take into account how the conclusion relates to the rest of the argument or if the conclusion follows the pattern you're looking for?

Great exercise!

Excited to learn more about logical reasoning!

the context should be more to just set up the conclusion and premise; I think the conclusion and premise should be more closely related

I think premise will more directly support the conclusion, but context won't as much, it'll just set up the rest of the passage, I think.