【正确答案】 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)and emphysema(肺气肿)，but this has yet to be proven”。那么可见该题答案应该是D，smog and chronic bronchitis and emphysema。本题完全是根据原文原句做答；只是用同义词determine代替了prove。