You are given a sentence, a question and two answer options ('A' and 'B'). Your task is to find the correct answer (return the string of the correct option, not 'A' or 'B') for the given question.
Example: Sentence: Jacob and Benny are squatting at the gym. Jacob has thin frail legs and Benny has big strong legs. Question: Who squats less weight? (A) Jacob (B) Benny
Example solution: Jacob
Example explanation: Typically, people with thin frail legs squat less weight than people with big strong legs, so the answer is Jacob.

Problem: Sentence: A dirty tooth isn't as smooth as a clean tooth. Question: Which surface will a toothbrush move over at a greater rate of speed? (A) dirty tooth (B) clean tooth

Solution: clean tooth