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: Which of these objects is translucent?  
 (A) A student's notebook (B) A mirror on the bus (C) A brick wall of the school (D) A student's sunglass lenses
Example Output: D

Example Input: The fur of some animals becomes thicker in the winter and is shed in the spring. These observations show how animals  
 (A) respond to changes in the environment (B) move from place to place to survive (C) store fat for the winter (D) compete with other animals for food
Example Output: A

Example Input: All animals need food to survive. Immediately after an animal eats food, the food is  
 (A) stored for later use (B) converted into waste (C) transported by the bloodstream (D) digested into simpler substances
Example Output:
D