instruction:
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.
question:
If an ecosystem's balance is disturbed by a volcanic eruption, what will most likely occur?  
 (A) The ecosystem will not change from its original state. (B) The ecosystem will eventually become balanced again. (C) The consumers in the ecosystem will begin to consume carbon dioxide. (D) The consumers in the ecosystem will begin to produce more oxygen.
answer:
B


question:
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.
answer:
D


question:
The relationship between an owl and a mouse is a  
 (A) parasite-host relationship. (B) symbiotic relationship. (C) mutualistic relationship. (D) predator-prey relationship.
answer:

D