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:
When a cup of water at room temperature is put in a freezer, the water's state of matter will change from  
 (A) liquid to gas (B) gas to liquid (C) liquid to solid (D) solid to liquid

Ex Output:
C


Ex Input:
Which is an example of a chemical reaction?  
 (A) The melting of ice (B) The grinding of salt crystals to powder (C) The burning of wood (D) The evaporation of water from a puddle

Ex Output:

C