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.
--------
Question: Which of these is a structure that is present in all organisms?  
 (A) a tissue (B) a cell (C) a stomach (D) a brain

Answer: B


Question: Which of the following forms of energy is released or absorbed in most chemical reactions?      
 (A) light energy (B) electrical energy (C) sound energy (D) heat energy

Answer: D


Question: Which investigation might be used to demonstrate potential energy?  
 (A) Roll one ball toward another, and see what happens when they collide. (B) Place a glass of water in the freezer, and see how long the water takes to become solid. (C) Compress a spring by different amounts, and see how far it can launch a ball into the air. (D) Roll a ball from the top of an inclined plane and determine the amount of time it takes to get to the bottom.

Answer:
C