Instructions: You are given a science question (easy-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: What can we learn by studying fossils?  
 (A) how hurricanes formed long ago (B) how the solar system was formed (C) the cause of strong earthquakes (D) how Earth's environments have changed
Output:
D