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: 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

SOLUTION: C

PROBLEM: What is the name of the product formed from the reaction shown below? 4Fe(III) + 3O_{2} -> 2Fe_{2}O_{3}  
 (A) iron (II) oxide (B) iron (III) oxide (C) oxygen ferrite (D) diferrous trioxide

SOLUTION: B

PROBLEM: Which adaptation helps a bird fly?  
 (A) larger feet (B) bigger eyes (C) longer beaks (D) hollow bones

SOLUTION:
D