46. Why does the author say that one needn't be concerned about memory slips?
- A. Not all of them are symptoms of dementia.
- B. They occur only among certain groups of people.
- C. Not all of them are related to one's age.
- D. They are quite common among fifty-year-olds.
答案：A
答案句：We know the risk of dementia (痴呆症) increases with age. But if you have memory slips, you probably needn't worry. There are pretty clear differences between signs of dementia and age-related memory loss.
参考译文：我们知道痴呆症的风险随年龄增长而增加。但如果你有记忆失误，你可能不必担心。痴呆症的迹象和与年龄相关的记忆丧失之间有相当明显的区别。
定位线索：题干“Why does the author say that one needn't be concerned about memory slips”→答案句“But if you have memory slips, you probably needn't worry”和“There are pretty clear differences between signs of dementia and age-related memory loss”；文中“memory slips”对应题干“memory slips”；文中“pretty clear differences between signs of dementia and age-related memory loss”对应选项A“Not all of them are symptoms of dementia”（并非所有记忆失误都是痴呆症症状）。
解析：题干问为什么不必担心记忆失误，答案句明确指出记忆失误不必担心，因为痴呆症迹象和年龄相关记忆丧失有明显区别，即并非所有记忆失误都是痴呆症症状，对应A。B项“只发生在特定人群”无中生有；C项“与年龄无关”与原文“age-related memory loss”矛盾；D项“五十岁人群中很常见”是事实但不是原因，答非所问。
47. What happens as we become aged according to the passage?
- A. Our interaction skills deteriorate.
- B. Some parts of our brain stop functioning.
- C. Communication within our brain weakens.
- D. Our whole brain starts shrinking.
答案：C
答案句：The brain ages just like the rest of the body. Certain parts shrink, especially areas in the brain that are important to learning, memory and planning. Changes in brain cells can affect communication between different regions of the brain. And blood flow can be reduced as blood vessels narrow.
参考译文：大脑和身体其他部分一样衰老。某些部分会萎缩，尤其是大脑中对学习、记忆和规划重要的区域。脑细胞的变化会影响大脑不同区域之间的交流。随着血管变窄，血流量也会减少。
定位线索：题干“What happens as we become aged”→答案句取自第3段“The brain ages just like the rest of the body”；文中“Changes in brain cells can affect communication between different regions of the brain”对应选项C“Communication within our brain weakens”（大脑内部交流减弱）。
解析：题干问随着年龄增长会发生什么，答案句提到脑细胞变化影响大脑不同区域之间的交流，即大脑内部交流减弱，对应C。A项“互动技能恶化”无中生有；B项“部分大脑停止运作”程度过重，原文只说“affect”；D项“整个大脑开始萎缩”范围扩大，原文说“Certain parts shrink”（某些部分萎缩）。
49. What should people do when signs of serious memory loss show up?
- A. Check the brain's cognitive reserve.
- B. Stop medications affecting memory.
- C. Turn to a professional for assistance.
- D. Exercise to improve their well-being.
答案：C
答案句：You don't have to figure this out on your own. Daffner suggests going to your doctor to check on medications, health problems and other issues that could be affecting memory.
参考译文：你不必自己弄清楚这个问题。达夫纳建议去看医生，检查药物、健康问题和其他可能影响记忆的问题。
定位线索：题干“What should people do when signs of serious memory loss show up”→答案句“Daffner suggests going to your doctor”；文中“going to your doctor”对应选项C“Turn to a professional for assistance”（寻求专业帮助）。
解析：题干问出现严重记忆丧失迹象时该怎么做，答案句建议去看医生，即寻求专业帮助，对应C。A项“检查大脑认知储备”偷换概念，原文说“check on medications, health problems”而非认知储备；B项“停止影响记忆的药物”无中生有，原文只说“check on medications”；D项“锻炼改善健康”是预防建议，不是出现迹象后的做法，答非所问。