Please choose the correct answer to the question: 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

Answer1: wind and rain. Answer2: animal movement. Answer3: crops grown in the soil. Answer4: increased temperatures.

Answer format: answer1/answer2/answer3/answer4
Answer: answer1