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.

Ex Input:
Which example best illustrates an action-at-a-distance force?  
 (A) lifting a box (B) an apple falling (C) pulling a nail out of wood (D) a car moving along a flat surface

Ex Output:
B


Ex Input:
What is the complementary base to cytosine in DNA?  
 (A) uracil (B) thymine (C) guanine (D) adenine

Ex Output:
C


Ex 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

Ex Output:

A