Instructions: You are given a science question (hard-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D'. There is only one correct answer for each question.
Input: Which is most similar to the way a glacier makes a valley?  
 (A) A bulldozer pushes a pile of dirt. (B) A shoe makes a footprint in soil. (C) A tree root splits a rock in half. (D) A drill makes a hole in a board.
Output:
A