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: Fertilizers can enable farmers to grow the same crop in a field for several years in a row. Farmers who use less fertilizer often rotate their crops by planting the crop one year and legumes, such as beans and clover, the following year. Fertilizer use and crop rotation with legumes both increase the availability of which of the following nutrients in soil?  
 (A) calcium (B) nitrogen (C) oxygen (D) protein
Example Output: B

Example Input: Which statement about gravity is written as a law?  
 (A) The reason gravity works is because masses bend time and space. (B) The effect of gravity on plants might be reduced if certain minerals are added to the soil. (C) The force of gravity between two objects depends upon their masses and the distance between them. (D) The experiments being done on gravity today are better than what were done in the past and a full understanding is only a few years away.
Example Output:
C