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:
Humans use both renewable and nonrenewable resources. Which human activity uses a nonrenewable resource?  
 (A) building houses with wood (B) using natural gas to heat homes (C) using solar energy to power lights (D) producing electricity from flowing water
answer:
B


question:
When iron combines with oxygen in a moist environment, rust forms because of a  
 (A) chemical reaction. (B) physical reaction. (C) change in density. (D) change in temperature.
answer:
A


question:
While performing an experiment involving four different clear liquids, a student forgets to label the test tubes. What should the student do?  
 (A) try to identify the liquids by smell (B) ask another student to identify the liquids (C) ask the teacher how to dispose of the liquids (D) continue the experiment with the unidentified liquids
answer:

C