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: On a field trip, a student holds a frog and reports that it has slippery skin. This is an example of  
 (A) a measurement (B) a prediction (C) an explanation (D) an observation
Example Output: D

Example Input: Leather basketballs are made for indoor use on smooth surfaces. Rubber basketballs are made for use on many different surfaces. Which of the following properties of rubber makes it better than leather for use on many different surfaces?  
 (A) Rubber is durable. (B) Rubber is lightweight. (C) Rubber is dark in color. (D) Rubber is quickly produced.
Example Output:
A