Instructions: 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.
Input: Sentence: A halter sliding across a barn floor gets hotter then one sliding across a field. Question: Which surface forces the halter to travel at a lower rate of speed? (A) barn floor (B) field
Output:
barn floor