Choice C is the best answer. In Passage 1, Lincoln makes clear his belief that individuals should always heed the laws:"Let every American... swear... never to violate in the least particular, the laws of the country" (lines 1-4,"Let every...the country"). Even bad laws, he states, "while they continue in force, for the sake of example, they should be religiously observed" (lines 30-32,"should be...observed"). In Passage 2, Thoreau is less rigid in his beliefs regarding the need for individuals to heed the laws of the country, arguing at times that some laws should be broken: "but if it is of such a nature that it requires you to be the agent of injustice to another, then, I say, break the law" (lines 64-66,"but if...the law"). While Lincoln and Thoreau can therefore be said to disagree about the moral imperative to follow existing laws, both passages advance an opinion regarding the need to follow or not follow all of the country's laws.
Choice A is incorrect because the passages are not making arguments about differences between legal duties and moral imperatives but rather are addressing the need to follow (or not) the laws of a land. Choice B is incorrect. Both passages address the question of changing existing laws in the United States, but that is only a minor part of what is a greater debate about the need to follow or not follow existing laws. Choice D is incorrect because neither passage addresses the standards for determining whether or not laws are just, only whether laws should be heeded or not.