[解析]
(1)B.主旨大意题。根据第一段"Researchers at the University of Texas Southwestern Medical Center mapped brain changes after a year of aerobic workouts and uncovered a potentially significant process:Exercise increases blood flow into two key areas of the brain associated with memory.(德克萨斯大学西南医学中心的研究人员绘制了一年有氧锻炼后大脑的变化图,并发现了一个潜在的重要过程:锻炼增加了大脑中与记忆相关的两个关键区域的血液流量)"以及第二段"The study,published in the Journal of Alzheimer's Disease,showed this blood flow can help even older people with memory issues improve cognition,a finding that could guide future Alzheimer's disease research,according to UT Southwestern Medical Center.(据德克萨斯大学西南医学中心称,这项发表在《阿尔茨海默病杂志》上的研究表明,这种血液流动甚至可以帮助有记忆问题的老年人改善认知能力,这一发现可以指导未来的阿尔茨海默病研究)"可知,这项研究的主要内容是锻炼提高记忆力。故选B。
(2)D.细节理解题。根据第三段中"Brain imaging of the aerobic exercise group,taken while at rest at the beginning and end of the study,showed increased blood flew into the specific brain areas that played important roles in memory function.(有氧运动组在研究开始和结束时休息时进行的大脑成像显示,增加的血液流入了对记忆功能起重要作用的大脑特定区域)"可知,参与者经过一年的有氧运动后,更多的血液流入与记忆相关的区域。故选D。
(3)C.词句猜测题。根据倒数第二段中"Many teams across the world are trying to determine if aerobic exercise might fight memory loss.Evidence is growing that it could at least play a small role in delaying or reducing the risk of Alzheimer's disease.(世界各地的许多团队都在试图确定有氧运动是否可以对抗记忆丧失。越来越多的证据表明,它至少可以在延缓或降低阿尔茨海默病的风险方面发挥一点作用)";画线词上文"a 2018 study showed that people with lower fitness levels experienced faster"以及后文"of vital nerve fibers in the brain called white matter related to memory."可知,2018年的一项研究表明,健康水平较低的人大脑中重要神经纤维(与记忆有关的白质)衰退得更快,故画线词意思是"衰退"。A.Growth.增长;B.Recovery.恢复;C.Decline.下降,衰退;D.Extension.延伸。故选C。
(4)A.推理判断题。根据最后一段中""Blood flow in the brain connected with memory improvement is still a part of the puzzle,and we need to continue piecing it together," Thomas says.(托马斯说:"大脑中的血液流动与记忆改善有关,这仍然是谜题的一部分,我们需要继续把它们拼凑起来。")"可推知,需要做进一步的研究工作。故选A。