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: Similar types of cells form tissues. What is the next level of complexity formed from the grouping of tissues?  
 (A) organs (B) organelles (C) organisms (D) organ systems
Example Output: A

Example Input: At a weightlifting competition, two competitors lifted the same weight to the same height. The second competitor accomplished the lift 2 seconds faster than the first competitor. This demonstrated that the second competitor had more  
 (A) energy than the first. (B) inertia than the first. (C) power than the first. (D) work than the first.
Example Output: C

Example Input: Which organ system communicates with cells in muscle tissue so that the muscles contract or relax, allowing the body to move?  
 (A) circulatory system (B) nervous system (C) respiratory system (D) excretory system
Example Output:
B