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: Rocks that contain fragments of bones, shells, and plant remains are most likely  
 (A) crystals. (B) igneous. (C) sedimentary. (D) metamorphic.
Example Output: C

Example Input: The prairie grass ecosystem once had a deep layer of topsoil which was protected by the grasses that covered it. Removal of these grasses for farmland is causing the soil to be eroded mainly by  
 (A) wind and rain. (B) animal movement. (C) crops grown in the soil. (D) increased temperatures.
Example Output: A

Example Input: Which behavior is an example of an animal adapting to a change in the environment?  
 (A) a squirrel climbing a tree (B) a rabbit feeding its young (C) a frog eating an insect (D) a bird migrating south
Example Output:
D