You are given a science question (easy-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: An enclosed 20 mL metal cylinder was filled with a gas sample at room temperature. The sample then was transferred to an empty 40 mL enclosed container, also at room temperature. After being transferred, the volume of the gas was  
 (A) 10 mL. (B) 20 mL. (C) 30 mL. (D) 40 mL.
Example Output: D

Example Input: The body is made up of many systems that interact with one another. For example, the skeletal system and the muscular system work together to help the body move. Which system works with the respiratory system to distribute oxygen to the body?  
 (A) muscular system (B) digestive system (C) lymphatic system (D) circulatory system
Example Output: D

Example Input: If wolves prey on deer for food, what will most likely happen to the deer population if wolves are removed from an area where deer live?  
 (A) The population of deer will increase. (B) The population of deer will decrease. (C) The population of deer will remain the same. (D) The population of deer will become extinct.
Example Output:
A