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: A container is filled with a mixture of sand and an unknown substance. What should a student do to determine whether iron particles are in the mixture?  
 (A) heat the mixture (B) filter the mixture (C) pour water into the mixture (D) pull a magnet through the mixture

Output: D


Input: Consider Input: Many states require vehicles to be examined and to meet safety and pollution standards. What impact might vehicle inspections have on the environment?  
 (A) The environment will not be polluted. (B) The environment will become more polluted. (C) Fewer pollutants will be released by vehicles. (D) Fewer pollutants will be produced by older vehicles.

Output: C


Input: Consider Input: If a child scrapes his foot on a piece of rusty metal, it is important to get medical treatment because the  
 (A) metal is corrosive to the skin. (B) foot carries large amounts of bacteria. (C) foot is the most sensitive part of the body. (D) metal may be contaminated and cause infection.


Output: D