Detailed Instructions: 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.
Problem:A student compared the speeds at which a large and a small marble rolled down an inclined plane. In order to make the findings more reliable, the student should  
 (A) release the marbles at different heights. (B) repeat the experiment several times. (C) tilt the plane at different angles. (D) use two marbles that are the same size.
Solution:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
B