Older adults with a better sense of smell may live longer than those who have a poor sense of smell,

8. C    9. D    10. D    11. C
【解析】
这是一篇说明文。文章介绍了一项新的研究成果：嗅觉好的老人可能比嗅觉差的老人更长寿。
【8题详解】
细节理解题。根据第一段关键句“The study was a project of researchers in the United States that was continuing for over 13 years.”可知，这项研究是一个美国研究人员已经持续了超过13年的项目。由此可推断出，这个项目已经持续了超过13年了。故选C项。
【9题详解】
细节理解题。根据第二段关键句“When the study was started, none of the adults were weak. They could walk about half a kilometre, climb 10 steps and independently complete daily activities.”（当这项研究开始时，没有一个成年人身体虚弱。他们可以步行约半公里，爬10级台阶，独立完成日常活动。）可知，当研究开始时，所有的成年人都能独立进行日常活动。故选D项。
【10题详解】
细节理解题。根据倒数第二段关键句“This suggests that a poor sense of smell is an early and sensitive sign of worsening health before it is recognizable in medical tests.”可知，嗅觉差是健康恶化的早期迹象。再根据最后一段关键句“The results also suggest that a poor sense of smell may be an early warning of poor health in older age that goes beyond dementia (痴呆) or other neurodegenerative (神经变性的) diseases.”可知，嗅觉差是老年人健康状况不佳的早期预警。综上可知，老年人如果嗅觉差，就应该注意身体健康了。故选D项。
【11题详解】
词义猜测题。根据划线词所在句的前句“They asked nearly 2300 men and women to recognize 12 common smells.”可知，研究员让近2300名男性和女性去识别12种常见的气味。再根据划线词所在句句意可推断出，应该是上句提到的所有的实验对象的年龄是在71岁到82岁之间，故划线部分词汇意为实验对象。故选C项。