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 Q]: Which form of energy are x rays and ultraviolet light?  
 (A) nuclear (B) heat (C) electromagnetic (D) chemical
[EX A]: C

[EX Q]: Which difference between water and ice results in ice floating on cold water?  
 (A) heat (B) shape (C) density (D) volume
[EX A]: C

[EX Q]: The rate of acceleration of an object is determined by the mass of the object and   
 (A) the initial velocity of the object. (B) the forces acting on the object. (C) the direction of movement of the object. (D) the change in kinetic energy of the object.
[EX A]:
B