Q. “The first of which is better.” I said this is a sentence fragment, but a student pointed out that it has a subject and predicate. Who’s correct?
A. You both are. A sentence fragment can have a subject and predicate, but it’s a fragment if it’s dependent on another clause. Your fragment can’t stand alone grammatically; it needs a main clause to lean on: “The choice is between a hamantash and a latke, the first of which is better.”