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: In 2014, a break in a storm water pipe released thousands of gallons of coal ash from a retired electrical plant into a river. The spill occurred upstream from the water treatment plants that serve communities along the river. Coal ash contains several hazardous metals including arsenic. Which stage of the water treatment process is most likely to remove hazardous metals from the water?  
 (A) aeration (B) coagulation (C) disinfection (D) reverse osmosis

Output: B


Input: Consider Input: The visible colors listed from shortest to longest wavelength are violet, blue, green, yellow, orange, and red. Which of the following accurately compares the frequency of these colors using this information?  
 (A) Blue has a higher frequency than violet. (B) Blue has a higher frequency than green. (C) Orange has a lower frequency than red. (D) Violet has a lower frequency than yellow.

Output: B


Input: Consider Input: An astronaut drops a 1.0 kg object and a 5.0 kg object on the Moon. Both objects fall a total distance of 2.0 m vertically. Which of the following best describes the objects after they have fallen a distance of 1.0 m?  
 (A) They have each lost kinetic energy. (B) They have each gained the same amount of potential energy. (C) They have each lost the same amount of potential energy. (D) They have each gained one-half of their maximum kinetic energy.


Output: D