instruction:
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.
question:
The skin is the largest organ in the human body. Why is skin considered to be an organ?  
 (A) It is made of cells. (B) It acts as a barrier. (C) It is made of tissues. (D) It is part of an organism.
answer:
C


question:
When a dog sees a cat, a message travels from the dog's eyes to the dog's  
 (A) brain (B) nose (C) paws (D) muscles
answer:
A


question:
Which of the following is the farthest from Earth?  
 (A) Halley's comet (B) the Andromeda galaxy (C) Neptune (D) the Sun
answer:

B