第33题: [单项选择]The relationship between exposure to ______ has not yet been determined. A. ozone and fall in lung function B. ozone and lung diseases such as asthma C. nitrogen dioxide and worse lung function D. smog and chronic bronchitis and emphysema 参考答案:D 答案解析:判断依据是来自原文中的一句话“It is suspected that long-term exposure to smog may result in chronic bronchitis(支气管炎