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:
How does sedimentary rock form?  
 (A) sediments cool (B) sediments melt (C) sediments separate (D) sediments compress

Ex Output:
D


Ex Input:
Compost piles have many parts, such as leaves, moisture, vegetables, and microorganisms. Which part of a compost pile breaks down materials and adds nutrients to the soil?  
 (A) leaves (B) moisture (C) vegetables (D) microorganisms

Ex Output:
D


Ex Input:
The human body is composed of different systems made of specialized cells, tissues, and organs. Each of these structures has a specific function that aids in the survival of the human species. Which organs are used in reproduction?  
 (A) brain, spinal cord, and eyes (B) lungs, esophagus, and heart (C) mouth, stomach, and gallbladder (D) ovaries, uterus, and fallopian tubes

Ex Output:

D