Hi mokkyukkyu,
Thanks for your question!
The first sentence is a principle because it is a general proposition that serves as the foundation for a certain chain of reasoning that concerns the criminal justice system. It's also a normative statement, ascribing the need to guarantee a particular outcome in that system.
Contrary to what you seem to suggest, the first and the second sentences are not saying the same thing at all. Whereas the first sentence outlines a general mandate, the second sentence examines the implications of that mandate. As such, the first sentence contains the premise for this argument; the second sentence is the conclusion:
Premise: Legal system remain just lawbreakers cannot have an unfair advantage over law abiders.
Conclusion: Criminal punishment must try to ensure that criminals do not profit from their crimes.
The Method-AP question asks about the function of the first sentence, which - as explained - is a principle offered in support for the conclusion.
Answer choice (B) is therefore correct.
Answer choice (A) is incorrect, because this condition will not
ensure that the legal system remains just. This answer choice seems to suggest the following:
- lawbreakers cannot have an unfair advantage over law abiders Legal system remain just
This is clearly a Mistaken Reversal of the principle (see above). Nothing will necessarily ensure a just legal system: ensuring that lawbreakers don't have an unfair advantage is a necessary, not a sufficient, condition for this outcome. Thus,
if the system is to remain just, the condition referenced in the stem must be met.
Hope this clears it up!
Thanks,