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.

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


[Q]: Marta studied different forms of energy. Which two types of energy travel in waves?  
 (A) light and sound (B) electrical and sound (C) chemical and light (D) chemical and electrical
[A]: A


[Q]: A snail's shell provides the snail with  
 (A) food. (B) energy. (C) protection. (D) transportation.
[A]:
C