You will be given a definition of a task first, then some input of the task.
You are given a science question (hard-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.

An atom can best be described as  
 (A) the smallest particle that has all the characteristics of a compound. (B) the smallest particle that has all the characteristics of an element. (C) a charged particle that is similar to a molecule. (D) a charged particle that is larger than a molecule.
Output:
B