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 Q]: 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 A]: A

[EX Q]: To study the effect of heat on plant growth, Andy divided ten identical seedlings into groups. She placed one group on a windowsill in the sun and the other group in a dark closet on the cool (north) side of the house. Think about the characteristics of a properly designed scientific experiment. What is wrong with the above experiment?  
 (A) The temperature difference between the two groups was not great enough. (B) The amount of light was different for the two groups. (C) One group of seedlings got less water than the other. (D) Nothing is wrong with the experiment.
[EX A]: B

[EX Q]: Mountains are most likely formed  
 (A) when glaciers melt. (B) from earthquakes. (C) when land sinks. (D) along tectonic plates.
[EX A]:
D