<p>my read is that there's no error.</p>
<p>The valuable stringed instruments in this display,
all more than 300 years old, were carefully crafted
by famous artisans in their day but long since
forgotten.</p>
<p>The sentence doesn't lend itself to the interpretation that the artisans were forgotten... How would it make sense to say "famous artisans in their day but long since forgotten?" There's is no "that + verb" to suggest is was the artisans, as in, "famous artisans that were long since forgotten." </p>
<p>I'll agree with you that the "their" is ambiguous, though the rest of the sentence serves as a modifier that indicates its the instruments' day, not the artisans'. In any case, the "their" isn't underlined nor is any other questionable part of the sentence. No error.</p>
<p>I'm not sure there's really a grammatical error, but I agree with NJres, it sure is a mess stylistically. </p>
<p>"famous artisans in their day" is not idiomatic
"artisans famous in their day" on the other hand is perfectly idiomatic, since it keeps the often used phrase "famous in their day" together. An acceptable sentence just flips the two words "famous" and "artisans":</p>
<p>The valuable stringed instruments in this display,
all more than 300 years old, were carefully crafted
by artisans famous in their day but long since
forgotten.</p>
<p>(but that doesn't seem to have been college board's fix)</p>
<p>tl;dr</p>
<p>no single question is gonna pull ur score up 30-40 pts. it might not even change your score. 10 pts maybe and id only go through the trouble if it would put u in the next scoring bracket.</p>