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: 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 material is the best conductor of heat at room temperature?  
 (A) air (B) water (C) sulfur (D) copper

SOLUTION:
D