<p>I would go as far as to say that the strict definitions of the words <em>should</em> be enough. Even if all you were armed with were the definitions, I fail to see how “caustic” has any <em>direct</em> support.</p>
<p>I think “caustic” is only attractive because we can look at all the examples the author puts forth and think, “Wow, those sound really bad and intense. Hey, so does ‘caustic’ so I’ll choose that answer,” which unfortunately doesn’t really address the tone directly.</p>
<p>Anyways, we’re beating a dead horse at this point, but I think the important takeaway here, for prospective test-takers, is the sort of logic with which you should be assessing these questions.</p>