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]: Four students tried to find out which magnet was the strongest. They each shared one idea. Which idea shows scientific thinking?  
 (A) We can pick the longest magnet. (B) We can pick the heaviest magnet. (C) We can measure the strength of the magnets. (D) We can vote for the magnet that we think is the strongest.
[A]: C


[Q]: Scientists today understand how forces work due to Isaac Newton's study of  
 (A) electricity. (B) magnetism. (C) atoms. (D) gravity.
[A]:
D