有一位旅行家，在元朝时来到中国，深得元世祖忽必烈的赏识，被委以重任，在中国一住就

陈某租赁了徐某的房屋，租赁期间，徐某将房屋卖给了王某，出卖前，徐某未通知陈某，以下说法正确的是()

A．合同有效

B．合同无效

C．合同效力待定

D．合同可撤销

下图为叶肉细胞内进行的某些生理活动示意图，其中①、②为相关气体，A为叶肉细胞内的相关结构。请回答：

（1）在叶绿体中进行的生理活动是          作用，①代表的气体为         。

（2）[A]代表的结构为              ，该处进行的生理活动为        作用。该生理活动能分解       ，并释放出能量，供生命活动利用；从生态学角度分析，其释放的能量最终来源于        。

（3）将叶片放入酒精中隔水加热，会看到酒精变成绿色，说明叶绿体中的       已经溶解在酒精中。

（4）要证明②是哪种气体，可利用该气体                             的特性。

境内机构经常项目外汇账户的限额统一采用（）核定。

A.人民币

B.美元

C.英镑

D.欧元

足月新生儿出生后开奶的时间为（）

A.出生后1小时之内

B.出生后2小时

C.出生后4小时

D.出生后10小时

E.出生后24小时

Going to the ballpark, visiting friends and playing bingo are simple diversions for many of us. But for the elderly, these social pastimes may play a critical role in preserving their physical and mental health.

(46) In fact, a new study suggests that the less time older people spend engaged in social activity, the faster their motor function tends to decline. "Everybody in their 60s, 70s and 80s is walking more slowly than they did when they were 25," says Dr. Aron Buchman, a neurologist at the Rush University Medical Center in Chicago and leading author of the study, which was published in the June 22nd issue of the Archives of Internal Medicine. (47) "Our study shows the connection between social activity and motor function--and opens up a whole new universe of how we might intervene. "

(48) An increasing body of evidence has suggested that participating in mentally stimulating activity, socializing frequently and exercising may help protect against age-related decline-at least cognitive decline. As early as 1995, neuroscientist Carl Cotman, who studies aging and dementia at the University of California at Irvine, published a paper in Nature showing that physical exercise produces a protein that helps keep neurons from dying and spurs the formation of new neural connections in the brain. (49) More recently, Cotman demonstrated in studies of elderly dogs and mice that enriching their social environment is associated with improvement in brain function.

Researchers are also finding that social activity may be linked to the same protective effect in people. A recent study of 2 500 adults ages 70 to 79, published in the journal Neurology, found that those who were able to stay mentally sharp were also those who exercised once a week or more, had at least a ninth grade literacy level and were socially active.

While further research needs to be done to establish the exact impact of social activity and exercise on specific age-related declines (50) it’s likely that a reduction in social activity may simply be a symptom of physical decline, since people may naturally withdraw from social engagement as they lose motor skills-most researchers would agree that it is not unreasonable to encourage seniors to get out there more. Only 10% of people over 65 get the recommended amount of exercise (at least 2. 5 to 5 hours a week), and given that seniors already tend to be more socially isolated than younger adults, it’s difficult to motivate them to become more active. "If you are alone, you are less likely to follow recommendations," notes Verghese. It might help, though, if you visit Grandma more often and let her know that a regular pastime may just help her stay fitter and sharper longer.

(48) An increasing body of evidence has suggested that participating in mentally stimulating activity, socializing frequently and exercising may help protect against age-related decline-at least cognitive decline.