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]: A girl signals her friend by shining a flashlight on a mirror. Her friend can see the signal because  
 (A) heat energy can be transferred from one object to another (B) mechanical energy can be transferred from one object to another (C) sound energy can be reflected from one object to another (D) light energy can be reflected from one object to another
[EX A]: D

[EX Q]: Which particle type can be identified as being from a specific element?  
 (A) electron (B) atom (C) neutron (D) proton
[EX A]: B

[EX Q]: What type of force keeps the planets orbiting the Sun?  
 (A) gravitational (B) magnetic (C) electrical (D) nuclear
[EX A]:
A