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: Which two body systems are involved in inhaling oxygen and exhaling carbon dioxide?  
 (A) endocrine and skeletal (B) excretory and nervous (C) circulatory and respiratory (D) digestive and reproductive

Answer: C


Question: What is a decomposer?  
 (A) a living thing that breaks down dead organisms (B) a living thing that makes its own food (C) an animal that eats live plants (D) an animal that hunts other animals

Answer: A


Question: The measure of the amount of light received on Earth from a star is known as  
 (A) parallax. (B) redshift. (C) absolute magnitude. (D) apparent magnitude.

Answer:
D