TASK DEFINITION: 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.
PROBLEM: 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

SOLUTION: D

PROBLEM: The moon goes through phases as it revolves around Earth. During which phase of the moon would it be possible for a solar eclipse to occur?  
 (A) new moon (B) full moon (C) waning (D) waxing

SOLUTION: A

PROBLEM: A drinking water reservoir for a small town develops a blue-green algae bloom. The town hires a company to eliminate the problem. Which of the following should the company investigate first as a likely source of the problem?  
 (A) a pit where granite is ground up into gravel (B) a neighborhood where lawn chemicals are used (C) a junkyard where old cars are salvaged for parts (D) a grain elevator where corn and soybeans are stored

SOLUTION:
B