Definition: 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: Milo knows that a frozen lake is smoother than a grass field. This means that when he slides his paper plane across one of the two surfaces it will experience less friction. Question: Which surface is that? (A) frozen lake (B) grass field
Output:
frozen lake