Which punctuation change is correct The composer had a preponderance?

You need to add more to the sentence for it to be complete and grammatically correct. Here are a few options, depending on the intended meaning:

Option 1: Adding a noun

* The composer had a preponderance of talent. (This uses a noun to complete the sentence.)

Option 2: Adding a prepositional phrase

* The composer had a preponderance in the field of classical music. (This uses a prepositional phrase to complete the sentence.)

Option 3: Adding a clause

* The composer had a preponderance, which was evident in his complex compositions. (This uses a dependent clause to complete the sentence.)

Without more context, it's impossible to say which punctuation change is *correct*.