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.

Ex Input:
An astronomer is studying two stars that are the same distance from Earth. Star X appears brighter than star Y. Which statement best explains this observation?  
 (A) Star X is larger than star Y. (B) Star Y is larger than star X. (C) Star X reflects the Sun’s light better than star Y. (D) Star Y reflects the Sun’s light better than star X.

Ex Output:
A


Ex Input:
Which best demonstrates that waves transfer energy?  
 (A) a bell ringing in a tower (B) a leaf falling from a tree (C) a ball rolling down a hill (D) a flag moving in the wind

Ex Output:
A


Ex Input:
Animals use resources in the environment to survive. Which of the following resources does an animal use for energy?  
 (A) air (B) food (C) shelter (D) water

Ex Output:

B