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]: Where do good bacteria grow to help keep people healthy?  
 (A) in the brain (B) in the blood (C) on the skin (D) on the bones
[EX A]: C

[EX Q]: Which form of energy is found in food?  
 (A) chemical (B) electrical (C) sound (D) mechanical
[EX A]: A

[EX Q]: A student wants to compare the masses and volumes of three marbles. Which two instruments should be used?  
 (A) Balance and graduated cylinder (B) Centimeter ruler and thermometer (C) Graduated cylinder and centimeter ruler (D) Thermometer and balance
[EX A]:
A