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: Jeannie put her soccer ball on the ground on the side of a hill. What force acted on the soccer ball to make it roll down the hill?  
 (A) gravity (B) electricity (C) friction (D) magnetism

Answer: A


Question: Oxygen reacts with iron to produce rust and with hydrogen to produce water. Which statement describes both reactions?  
 (A) A different mixture is formed in each case. (B) A different solution is formed in each case. (C) Both a change of state and of elements is involved. (D) New molecules are formed but the same elements exist.

Answer: D


Question: Which of the following is a typical example of a unicellular organism?  
 (A) earthworm (B) bacteria (C) fungi (D) green algae

Answer:
B