You are given a science question (hard-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: One example of a living thing is  
 (A) air (B) water (C) a rock (D) a worm

A: D
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Q: Which statement best compares single-celled and multi-celled organisms?  
 (A) Tissues in a single-celled organism are like the cells in a multi-celled organism. (B) The nucleus in a single-celled organism is like the skin of a multi-celled organism. (C) Organelles in a single-celled organism are like the organs in a multi-celled organism. (D) The cytoplasm in a single-celled organism is like the nervous system in a multi-celled organism.

A: C
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Q: An airplane takes off from Boston for the 980 km trip to Detroit. The plane lands two hours later. Which of the following best describes the average speed and direction of the airplane's flight?  
 (A) 325 km/h W (B) 490 km/h W (C) 980 km/h W (D) 1960 km/h W

A:
B
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