Use reasoning to answer the following question. What harms the respiratory and circulatory systems?\nOptions:\n- (A) oil\n- (B) rain\n- (C) sulfur\n- (D) cars\n- (E) tires\n- (F) coal\n- (G) tar\n- (H) bicycles
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Air pollution harms the respiratory and circulatory systems. Cars are a significant source of air pollution. Cars harm the respiratory and circulatory systems.
So, the answer is (D).
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