You are given a science question (easy-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:
Eyeglasses help a nearsighted person see as a result of  
 (A) absorption. (B) diffraction. (C) reflection. (D) refraction.

Ex Output:
D


Ex Input:
A bright object with a long tail of glowing gases is in orbit around the Sun. This object is most likely  
 (A) a planet (B) a star (C) an asteroid (D) a comet

Ex Output:
D


Ex Input:
A hot pack is a product that releases heat when chemicals inside of it interact. What is taking place inside an active hot pack?  
 (A) electric current (B) a net loss of mass (C) thermal insulation (D) an exothermic reaction

Ex Output:

D