Detailed 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.
Problem:Sentence: A valley is significantly rougher than a mountainside. Question: This means that lava rolling down which surface will reach a greater top speed? (A) mountainside (B) valley
Solution:
valley