Incorrect answer explanation

Thanks for your question @Will-Wester Answer choice A says that vaguely-defined terms "CANNOT serve a basis:" for provisions in documents in international law. But we know from Passage A that the vaguely-defined terms DO serve as the basis for provisions contained in UN Documents. The use of vague terms may be detrimental or ineffective, but that does not meant that they "CANNOT serve as a basis."

That is such a ridiculous approach to answer A. Just because they are trying to use it as a definition for international law doesn't mean it has internal consistency, and that doesn't fit the definition of "can".

Hi, I think this comes down to how one interprets the word "can." It sounds like you're reading it to mean should, in which case A would look quite good. However, A does not say should. It is indeed possible for this to be the case, even if it is less than ideal. Ultimately, A does not reflect a core principle of the first passage.