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(单选题)According to the author, mathematics is ______. (单选题)The difference between “fact” and “theory” ______. (单选题)According to the author, one possible reason for the growth (单选题)The title that best expresses the ideas of this passage is _ (单选题)How did the nineteenth-century defenders of photography stre (单选题)Why does the author introduce Abstract Expressionist painter (单选题)Which of the following adjectives best describes “the concep (单选题)What is the author mainly concerned with? The author is conc (单选题)What is the main purpose of the passage? (单选题)At the end of the passage the author proposes more work on _