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]: Which lists the diameter of the planets in order from smallest to largest?  
 (A) Venus, Earth, Mercury, Mars (B) Earth, Mars, Venus, Mercury (C) Mars, Mercury, Earth, Venus (D) Mercury, Mars, Venus, Earth
[EX A]: D

[EX Q]: Which series correctly represents the levels of organization in an organism?  
 (A) cells -> organs -> organ system -> tissue (B) cells -> tissue -> organs -> organ system (C) tissue -> cells -> organ system -> organs (D) tissue -> organ system -> cells -> organs
[EX A]: B

[EX Q]: Which system supports the body, protects internal organs, and makes blood cells?  
 (A) muscular system (B) circulatory system (C) nervous system (D) skeletal system
[EX A]:
D