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: When oxygen combines with hydrogen, which substance is formed?  
 (A) water (B) vinegar (C) hydrochloric acid (D) hydrogen dioxide

SOLUTION: A

PROBLEM: Which of the following statements best explains how the decomposition of plant and animal matter helps to form rich soils?  
 (A) Decomposition adds silt to soil. (B) Decomposition adds water to soil. (C) Decomposition adds oxygen to soil. (D) Decomposition adds nutrients to soil.

SOLUTION: D

PROBLEM: People use many tools to help measure changes. Which person is measuring a change?  
 (A) A sports player scores a goal. (B) A scientist gives a weather report. (C) A friend watches a television show. (D) A nurse checks the temperature of a patient.

SOLUTION:
D