You are given a sentence, a question and two answer options. Your task is to write down the index ('A' or 'B') of the **incorrect** option for the given question.
Q: 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
A: 
B