by Sage Pearce-Higgins Sat Jun 01, 2019 11:49 am
I agree with you that the term 'un-American' may be unfamiliar to some GMAT test-takers and that the problem assumes an equivalence between 'un-American' and 'contrary to the traditions of American culture and law'. However, I think that the problem still works for a couple of reasons.
The term 'un-American' is not so specific as to be familiar only to American students. It has an established usage in historical and cultural literature and could fall under the category of general vocabulary.
Even if a test-taker were unfamiliar with the term, it's more reasonable to interpret it as 'contrary to the traditions of American culture and law' than 'describing something that the majority of Americans are not willing to do'. The second definition is oddly specific - i.e. more than 50% - and extends beyond simply 'uncustomary' or 'unpopular'. In fact, answer D is quite a specific claim about the American population in general, rather than a belief that the author's argument is resting on.