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.

Ex Input:
Which of these warms most of the air, water, and land on Earth?
(A) Coal (B) Electricity (C) Sunlight (D) Wind

Ex Output:
C

Ex 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

Ex Output:
B

Ex Input:
Mars is an inner planet and Jupiter is an outer planet. Which best describes the relationship between the two planets?
(A) They are made of the same materials. (B) They orbit the Sun in opposite directions. (C) They have the same orbital periods around the Sun. (D) They are located on opposite sides of the asteroid belt.

Ex Output:
D