You are given a science question (hard-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: Janette conducts an investigation to see which foods make her feel more fatigued. She eats one of four different foods each day at the same time for four days and then records how she feels. She asks her friend Carmen to do the same investigation to see if she gets similar results. Which would make the investigation most difficult to replicate?  
 (A) measuring the amount of fatigue (B) making sure the same foods are eaten (C) recording observations in the same chart (D) making sure the foods are at the same temperature
Example Output: A

Example Input: Amanda and Jake learned about kinetic and potential forms of energy within a simple electrical circuit. The circuit they are studying has a battery, wires, and a light bulb. Which is a form of potential energy in the circuit?  
 (A) chemical energy in the battery (B) light energy from the light bulb (C) heat energy lost from the electric wires (D) electrical energy moving through the light bulb
Example Output: A

Example Input: The following mathematical expressions represent four different concentrations of a chemical solution to be used in a science experiment. Which one is equal in magnitude to 1/1000?  
 (A) 1.0 x 10^3 (B) 1.0 x 10^4 (C) 1.0 x 10^-3 (D) 1.0 x 10^-4
Example Output:
C