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: A scientist uses angstrom units to measure the distance between two points. The scientist is most likely measuring the distance between two  
 (A) atoms. (B) cities. (C) continents. (D) stars.
Example Output: A

Example Input: Which organ is made mostly of muscle?  
 (A) heart (B) lung (C) ear (D) brain
Example Output: A

Example Input: What is the main source of raw material for the production of plastics?  
 (A) clay (B) plants (C) petroleum (D) sand
Example Output:
C