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.

Example Input: In a lab experiment, students are testing the identity of an unknown powder. Which method is most appropriate to move the powder to a balance?  
 (A) sweep with a brush onto transfer paper (B) scoop with lab spatula onto transfer paper (C) pinch with fingers and lift onto transfer paper (D) pour from bottle onto transfer paper
Example Output: B

Example Input: Many scientists think that burning fossil fuels has increased the amount of carbon dioxide in the atmosphere. What effect would the increase of carbon dioxide most likely have on the planet?  
 (A) a cooler climate (B) a warmer climate (C) lower relative humidity (D) more ozone in the atmosphere
Example Output: B

Example Input: What are two ways ice can change Earth's surface?  
 (A) cracking a rock and making a U-shaped valley (B) making a dune and making a U-shaped valley (C) making a dune and making a V-shaped valley (D) cracking a rock and making a V-shaped valley
Example Output:
A