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

Answer: A


Question: Which material is most easily recycled at school?  
 (A) plastic wrap (B) notebook paper (C) ice cream sticks (D) rubber erasers

Answer: B


Question: The energy that is stored in food originally comes from  
 (A) air (B) soil (C) sunlight (D) water

Answer:
C