This principle contains a value judgment about fairness. It's also triggered by Mary's factual premise; her statement that every speeding driver was equally likely to be ticketed matches the principle's sufficient condition. And finally, the principle leads to the correct conclusion: the principle justifies Mary's claim that the ticket was fair.

This principle doesn't make any judgment about fairness, which is essential to bridge Mary's premises to her conclusion.

This principle doesn't contain a value judgment about fairness, which is something we need in the correct answer. And even if we assume that "should" counts as a judgment of fairness, this principle doesn't lead to the right conclusion: the officer didn't punish everyone who was speeding, and yet Mary concludes that the officer acted fairly.

This has a value judgment about fairness, but it goes the wrong way—it leads to the wrong conclusion. Because the officer only enforced the law against John, and not the other speeding drivers, this principle would tell us the officer acted unfairly.

Like (D), this principle gives us a value judgment about fairness, but it also leads to the opposite conclusion than Mary's argument. This principle would tell us that the officer's behavior was unfair because of not penalizing all speeding drivers equally.