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(单选题)Where is the passage extracted? (单选题)From the last two paragraphs we can infer that. (单选题)The underlined word “they” in paragraph 6 refers to. (单选题)Why smog has become a common concern? (单选题)The effect of smog doesn’t include______. (单选题)What is the main purpose of this story? (单选题)What can we learn from the passage? (单选题)How did the doctor know that the man burnt his knee? (单选题)What was the doctor doing? (单选题)Where did the story happen?