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:
A research study concluded that people who work longer hours increase their chances of having higher blood pressure. This conclusion was developed from a study of 200 men of different ages. How is this investigation biased?  
 (A) The sample size was too large. (B) Scientists did not run the study. (C) Women were excluded from the study. (D) No medication was given to the men.

Ex Output:
C


Ex Input:
In mice, a certain species displays incomplete dominance in coat coloring. The offspring of a black (BB) mouse and a white (bb) mouse are gray (Bb) mice. A cross between two gray mice will most likely produce offspring with which percent of coat colors?  
 (A) 25% black, 75% gray (B) 25% gray, 75% white (C) 25% white, 25% black, 50% gray (D) 25% gray, 25% black, 50% white

Ex Output:
C


Ex Input:
What is the relationship between a community and a population?  
 (A) A population is smaller than a community. (B) A population is larger than a community. (C) A population includes communities of organisms interacting. (D) A community includes populations of organisms interacting.

Ex Output:

D