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: Which of the following units best represents the density of an object?  
 (A) kg (B) hr (C) m/s^2 (D) g/cm^3

Output: D


Input: Consider Input: When nitrogen-rich runoff from farms enters a nearby farm, it causes abundant growth of algal mat on the pond surface. As a result, underwater plants in the pond begin to die. Identify the limiting factor that is most responsible for causing the underwater plants to die.  
 (A) oxygen (B) sunlight (C) nitrogen (D) carbon dioxide

Output: B


Input: Consider Input: The winter solstice occurs on either December 21 or 22, depending on the year. Which of the following statements best explains why the time of the year the winter solstice occurs has the least amount of daylight in Massachusetts?  
 (A) Earth is farthest away from the Sun on the winter solstice. (B) Earth's rotational speed on its axis is greatest on the winter solstice. (C) Earth is traveling around the Sun with the greatest speed on the winter solstice. (D) Earth's Northern Hemisphere is tilted away from the Sun on the winter solstice.


Output: D