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.

Example Input: When iron combines with oxygen in a moist environment, rust forms because of a  
 (A) chemical reaction. (B) physical reaction. (C) change in density. (D) change in temperature.
Example Output: A

Example Input: What is the MAJOR reason Earth has seasons?  
 (A) Earth has a moon (B) Earth has a tilted axis (C) Earth has a magnetic field (D) Earth has an elliptical orbit
Example Output: B

Example Input: Sedimentary rock helps scientists piece together the history of Earth most likely using clues from  
 (A) humus. (B) soil. (C) gravel. (D) fossils.
Example Output:
D