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.

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.

A: A
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Q: Which could be a possible way to prevent wildlife species from becoming endangered?  
 (A) drinking less water (B) establishing more habitats (C) cutting down more forests (D) stopping underground coal mining

A: B
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Q: Which type of organism is at the lowest level of the food chain?  
 (A) autotroph (B) heterotroph (C) carnivore (D) omnivore

A:
A
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