<p>I'd bet money on "knows something about jewelry."</p>
<p>IMO, there is a concrete reason why jewelry is correct and "detest" is wrong.</p>
<p>Jewelry (correct): states that the author knows a good est. of the jewelry's value. It never says he directly knows something about jewelry, so it is in fact implied, although obvious.</p>
<p>Detest (incorrect): detest means to abhor. There is nothing concrete enough in the passage to suggest an attitude as negative as "abhor," especially in the context of his criticisms primarily serving as justifications for his actions.</p>