[判断题] 实验动物设施的窗:屏障环境多不设外窗或尽可能少设窗。一般动物除需要自然采光与通风的场所外,不宜设置外窗。设有外窗的动物室,如猴类动物房,应在墙上加设栏栅和铁丝网以防止动物逃跑。寒冷地区窗上有防结霜措施。在非清洁区设置的外窗,尽量做到气密性完好。 ( )
A.正确
B.错误

Samuel H. Preston, a sociologist at the University of Pennsylvania, studied how the American family is changing. He reported that by the time the average American couple reaches 40 years of age, they have more parents than children. This finding shows the change in lifestyles (生活方式) and duties of aging Americans. The average middle-aged couple can look forward to caring for elderly parents some time after their own children have grown up.
Because Americans are living longer than ever, more researchers and social workers have begun to study care giving to improve care of the elderly. When people care for an elderly relative, they often do not use community (社区) services, such as adult (成人) daycare centres. If the care givers are adult children, they are more likely to use such services, especially because they often have jobs and other business. However, the wife of an elderly person is much less likely to use support services or to put the dependent person in a nursing ho
A. The sick.
B. The poor.
C. The parents.
D. The adult children.

IEEE802定义的局域网参考模型中；只包括了物理层和数据链路层，其中LLC通过其LLC地址为高层提供服务访问的接口，这个接口是 (71) 。在LLC帧中，广播地址是通过 (72) 表示的，将数据链路层划分成LLC和MAC的主要目的是 (73) 。在CSMA/CD传输控制方式中，冲突次数多的一个帧，其发送的优先程度 (74) 。在DQDB协议中，一个站点得到一个空时槽时，它可以使用或放过，这是通过 (75) 。