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]: A student wants to organize a group of animals into two categories based on observable external features. Which display will most appropriately show the two categories of animals?
(A) a timeline (B) a pie chart (C) a data table (D) a line graph
[EX A]: C

[EX Q]: Dr. Wagner is investigating a newly discovered, disease-causing agent. She determines that one structure in the agent is double-stranded RNA. What kind of agent is Dr. Wagner studying?
(A) a virus (B) a protist (C) a fungus (D) a bacterium
[EX A]:
A