Sentence :
She is one of those gifted writers who (turns, turn) out one best seller after another.
My answer is: turns. As we are talking about she, singular third person.
But the correct answer says: turn.
Sentence :
She is one of those gifted writers who (turns, turn) out one best seller after another.
My answer is: turns. As we are talking about she, singular third person.
But the correct answer says: turn.
Here is your example sentence, with the relevant part in bold:
She is one of those gifted writers who turn out one best seller after another.
In this context, it is the gifted writers (plural) in question who turn out bestsellers, and she is apparently a member of that club of bestselling writers.
So, turn it is.