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.

Ex Input:
Kim lost her hammer outside. When she found it a few months later, some parts of the metal were covered with flaky, brown rust. Which type of change occurred when rust formed on the hammer?  
 (A) chemical (B) electrical (C) thermal (D) physical

Ex Output:
A


Ex Input:
In the United States, which is responsible for ensuring the safety of the country's drinking water?  
 (A) Environmental Protection Agency (EPA) (B) Food and Drug Administration (FDA) (C) National Oceanic and Atmospheric Administration (NOAA) (D) Center for Disease Control (CDC)

Ex Output:
A


Ex Input:
One thing that all human cells have in common is that they  
 (A) control the brain. (B) make food. (C) move blood. (D) take in energy.

Ex Output:

D