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: Which of the following units best represents the density of an object?  
 (A) kg (B) hr (C) m/s^2 (D) g/cm^3
Example Output: D

Example Input: Which organisms contribute most to the decomposition of dead organisms?  
 (A) snakes (B) viruses (C) insects (D) bacteria
Example Output: D

Example Input: A paramecium is an example of  
 (A) a single-celled organism. (B) multiple organisms. (C) an inorganic substance. (D) a group of cells.
Example Output:
A