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 construction worker hit a solid steel wall with a sledgehammer, but the wall did not move. Part of the energy exerted by the worker  
 (A) was destroyed by the steel wall. (B) was converted into heat. (C) disappeared into the atmosphere. (D) was stopped by the hard surface.

Ex Output:
B


Ex Input:
Rhinoceroses and horses are related. They have very similar digestive systems and an odd number of toes on their feet. Horses have one toe, and rhinoceroses have three. These facts best support which claim?  
 (A) Horses and rhinoceroses share a common ancestor. (B) Horses and rhinoceroses are genetically identical. (C) Horses are the ancestors of modern rhinoceroses. (D) Horses have descended from modern rhinoceroses.

Ex Output:
A


Ex Input:
A student walking through the forest notices moss growth increases as the density of the forest increases. The student has made  
 (A) a hypothesis. (B) a conclusion. (C) an assumption. (D) an observation.

Ex Output:

D