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.

Q: Which two body systems are involved in inhaling oxygen and exhaling carbon dioxide?  
 (A) endocrine and skeletal (B) excretory and nervous (C) circulatory and respiratory (D) digestive and reproductive

A: C
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Q: Which of the following statements best explains why earthquakes occur more frequently in California than in Massachusetts?  
 (A) The rock found in California is igneous, but the rock found in Massachusetts is sedimentary. (B) California is located on the boundary of two crustal plates, but Massachusetts is not. (C) The rock under California is soft, but the rock under Massachusetts is hard. (D) California is located on a continental plate, but Massachusetts is not.

A: B
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Q: Which illness is associated with a weakened immune system in the body?  
 (A) tetanus (B) cancer (C) measles (D) rabies

A:
B
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