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.

Ex 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.

Ex Output:
A


Ex Input:
One important use of coal is to produce energy for homes. Coal can be burned and converted to  
 (A) wind energy. (B) nuclear energy. (C) electrical energy. (D) solar energy.

Ex Output:
C


Ex Input:
Which are replenished more quickly than they are used?  
 (A) energy resources (B) material resources (C) renewable resources (D) nonrenewable resources

Ex Output:

C