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:
Which organ is made mostly of muscle?  
 (A) heart (B) lung (C) ear (D) brain

Ex Output:
A


Ex Input:
Which unit of measurement describes an object's length?  
 (A) meter (B) kilogram (C) liter (D) degree

Ex Output:
A


Ex Input:
An object such as a hammer weighs less on the Moon than on Earth. This is because the Moon has a  
 (A) thinner atmosphere than Earth. (B) smaller diameter than Earth. (C) stronger magnetic field than Earth. (D) lower mass than Earth.

Ex Output:

D