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.

Example Input: Plants growing in a pond release a gas that fish need to survive. Which gas do the plants release that fish use?  
 (A) helium (B) hydrogen (C) nitrogen (D) oxygen
Example Output: D

Example Input: What is the function of skin on the human body?  
 (A) Skin has pores that help the body sense odor. (B) Skin protects the body from harmful substances. (C) Skin brings oxygen directly into the body's bloodstream.
Example Output: B

Example Input: Which type of energy is transferred from one object to another by simple machines?  
 (A) mechanical (B) chemical (C) nuclear (D) electrical
Example Output:
A