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: The relationship between ticks and a dog can best be described as  
 (A) mutualism. (B) competition. (C) parasitism. (D) commensalism.

Answer: C


Question: The most significant human-induced impact on Earth's atmosphere comes from the use of which energy resource?  
 (A) flowing water (B) fossil fuels (C) sunlight (D) winds

Answer: B


Question: Which statement best describes how the circulatory system and respiratory system can work together?     
 (A) Toxins are removed from the bloodstream by the liver. (B) The stomach signals for the production of gastric juices. (C) Food molecules are transported to the organs of the body. (D) Gases are exchanged between the lungs and blood vessels.

Answer:
D