I think I may have an answer. First, I think the question may have been phrased incorrectly. A tagline is normally a short, snappy line on the front cover of a book to get people interested in buying it. I think the intended term for this question is "dialogue tag," which means a word or phrase that can come before or after a line of dialogue that clarifies which character has just spoken. The most common dialogue tag is "said" (ex: "I'm sorry I can't help you," said Mrs. Brennan.)
In this case, I think the correct answer is the one that clearly states which character is delivering the line of dialogue.