Question 23 is based on the recording you have just heard.

原文：

Recording Three

W: A new study has failed to find any conclusive evidence that lifestyle changes can prevent cognitive decline in older adults. Still there are good reasons to make positive changes in how we live and what we eat as we age. (23)Cognitive decline is the loss of ability to learn new skills, or recall words, names, and faces that is most common as we age. To reduce or avoid it, researchers have examined the effect of smoking, diet, brain-challenging games, exercise and other strategies. Researchers at Duke University scrutinized more than 160 published studies and found an absence of strong evidence that any of these approaches can make a big difference. Co-author James Burke helped design the study.

M: "In the observational studies we found that some of the B vitamins were beneficial." "(24)Exercise, diet, cognitive stimulation showed some positive effects, although the evidence was not so strong that we could actually consider these firmly established."

W: Some previous studies have suggested that challenging your brain with mentally stimulating activities might help. And Burke says that actually does seem to help, based on randomized studies—the researcher's gold standard

M: "Cognitive stimulation is one of the areas where we did find some benefit. The exact type of stimulation that an individual uses is not as important as being intellectually engaged."

W: The expert review also found insufficient evidence to recommend any drugs or dietary supplements that could prevent or slow cognitive decline. However, given that there is at least some evidence for positive effects from some of these lifestyle changes, plus other benefits apparently unrelated to cognitive decline, Burke was willing to offer some recommendations.

M: "(25)I think that by having people adopt a healthy lifestyle, both from a medical standpoint as well as nutritional and cognitive stimulation standpoint, we can reduce the incidence of cognitive decline, which will be proof that these factors are, in fact, important."

W: James Burke of Duke University is one of the authors of a study reviewing previous research on cognitive decline. The paper is published online by the Annals of Internal Medicine.

23. According to the speaker, what might be a symptom of cognitive decline in older adults?

解析：A。录音开头女士提到，认知能力下降意味着丧失学习的能力，A选项中being unable to learn是对原文中the loss of ability to learn的同义替换，为正确答案。B选项“作出改变很缓慢”、C选项“越来越经常发脾气”和D选项“失去与他人相处的能力”均未提及，排除。