Please provide a longer explanation for #12 and using group 2 necessary rule.

Why would "Major Premise: No one could have been anywhere in the vicinity of a fire like that one and fail to notice it." be a "major" premise and not a minor one? Considering the fact the author is just interjecting that one could not fail to notice the fire. The minor premise only supports the vicinity not the "one could not fail to notice the fire."

How do you distinguish between most likely true vs. probably true? And does deciding a statement as strong inference vs weak inference lead to the difference between choosing a right answer or a wrong answer?