People sometimes dismiss a claim if it comes from a source they regard as self-interested, but

Choice B is the best answer because it most logically completes the text’s discussion about people’s tendency to dismiss claims from sources perceived as self-interested, or acting for their own advantage. In this context, "irrelevant" means not applicable to the matter at hand. The text explains that as a matter of logical reasoning, the source of a claim has nothing to do with the claim’s truthfulness—a claim is either true or false in actuality, regardless of where it originates. This context suggests that even though people may distrust a claim based on its source, the source of the claim is actually irrelevant.

Choice A is incorrect because in this context, "indistinct" would mean uncertain or not clearly recognizable. Instead of suggesting that the source of a claim can’t be determined with certainty, the text suggests that recognizing a source and having an opinion of it simply doesn’t matter because as a matter of logic, a claim is true or false in actuality, regardless of where it originates. Choice C is incorrect because in this context, "indisputable" would mean impossible to question or deny. Although the text suggests that it isn’t logical to assume a claim is false just because its source appears to be self-interested, it doesn’t go so far as to suggest that the source of a claim can’t be questioned—the text instead makes the point that from a logical standpoint, the source of a claim doesn’t matter because the claim is either true or false in and of itself. Choice D is incorrect because in this context, "implicit" would mean suggested or understood without being directly expressed. Nothing in the text suggests that logically, the source of a claim is only suggested; instead of addressing whether sources can be directly identified, the text focuses on the idea that sources don’t matter because a claim is true or false in actuality, regardless of where it originates.