Answer:
A. It may take me months, if not years, to train for a marathon.
Explanation:
Commas are a punctuation mark , used chiefly to show separation of words or word groups within a sentence.
The sentence that employs commas(,) correctly to balance a phrase would be as follows:
A). It may take me months, if not years, to train for a marathon.
Commas(,)
Thus, option A is the correct answer.
Learn more about "Comma" here:
brainly.com/question/8478728