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: Calcium carbonate (CaCO_{3}) is considered a compound because it is made up of two or more  
 (A) molecules. (B) elements. (C) gases. (D) solids.
Example Output: B

Example Input: Air is composed of many different substances. Which of the following components of air is a compound rather than an element?  
 (A) Argon, Ar (B) Oxygen, O2 (C) Water, H2O (D) Nitrogen, N2
Example Output: C

Example Input: Which material is primarily a mixture of weathered rock and organic matter?  
 (A) minerals (B) soil (C) ocean water (D) seashells
Example Output:
B