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.

Input: Consider Input: What occurs if the body's renal system fails to work?  
 (A) Gas exchange is impaired. (B) Blood oxygenation no longer occurs. (C) Metabolic waste builds up in the blood. (D) Nutrients are no longer transported to organs.

Output: C


Input: Consider Input: Which of these will result in the least gravitational attraction?  
 (A) two 2g objects 2 meters apart (B) two 2g objects 4 meters apart (C) two 1g objects 6 meters apart (D) two 1g objects 8 meters apart

Output: D


Input: Consider Input: When you make soap bubbles, what is inside the bubbles?  
 (A) Air (B) Soap (C) Water (D) Nothing


Output: A