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.

Input: Consider Input: A bright object with a long tail of glowing gases is in orbit around the Sun. This object is most likely  
 (A) a planet (B) a star (C) an asteroid (D) a comet

Output: D


Input: Consider Input: Melting, boiling, and freezing are examples of  
 (A) physical changes. (B) chemical changes. (C) magnetic changes. (D) electrical changes.

Output: A


Input: Consider Input: Which process moves an ion across a cell membrane against the concentration gradient?  
 (A) diffusion (B) exocytosis (C) facilitated diffusion (D) active transport


Output: D