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: Elephants on the African savanna eat shrubs and small trees. This behavior clears land and enables grass to grow. Grazers such as gazelles eat the grass. Lions prey on the gazelles. Which two organisms in this scenario are in the most cooperative relationship?   
 (A) the elephants and the shrubs (B) the shrubs and the lions (C) the elephants and the gazelles (D) the gazelles and the lions
Example Output: C

Example Input: A lake has been used for more than a century to irrigate crops. How has this practice most likely affected this resource?  
 (A) It decreased the salt content of the water. (B) It increased the evaporation rate of the water. (C) It increased the number of fish in the lake. (D) It decreased the volume of the lake.
Example Output: D

Example Input: When a compression wave travels through a medium, in what direction is the medium displaced?  
 (A) upward (B) downward (C) in the same direction (D) in the opposite direction
Example Output:
C