You are given a science question (hard-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.
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Question: Several horses grazed in a fenced area across from a home. On rainy days, soil would wash down a slope and run toward the home. After the horses were moved a few years later, the soil no longer washed down when it rained. What could account for this change?  
 (A) The grass grew and kept the soil intact. (B) The fence kept the soil contained. (C) The soil was completely gone. (D) The amount of rain decreased.

Answer: A


Question: A pharmaceutical company developed a drug to help relieve headaches. Recently, the pharmaceutical company discovered that the drug may cause nausea in a small number of people who might take the drug. Which is the most ethical course of action that the drug company could take?  
 (A) Discontinue the use of the drug. (B) Inform people of the possible side effects. (C) Reduce the amount of drug given to people. (D) Modify the drug to include medicine that prevents nausea.

Answer: B


Question: When a baby shakes a rattle, it makes a noise. Which form of energy was changed to sound energy?  
 (A) electrical (B) light (C) mechanical (D) heat

Answer:
C