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: 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: In one area, a large source of prey for eagles is rabbits. If the number of rabbits suddenly decreases, what effect will it most likely have on the eagles?  
 (A) Their numbers will increase. (B) Their numbers will decrease. (C) They will adapt new behaviors. (D) They will migrate to new locations.
Example Output: B

Example Input: An architect builds a 1/10 scale model of a house to test the design for sources of heat loss in the winter. Which part of the model would be most important to test with heat-sensing equipment?  
 (A) floors (B) ceilings (C) windows (D) staircases
Example Output:
C