下列哪一组高层系统服务可以提供对网络的访问控制()。
A、访问控制列表和访问特权
B、身份识别和验证
C、认证和鉴定
D、鉴定和保证
参考答案:B
工程建设具他费用包括()。
①土地使用费
②建设单位管理费
③工程保险费
④联合试运转费
⑤排污费
A.①②③④
B.①②③⑤
C.②③④⑤
D.①②④⑤
It is difficult to imagine what life would be like without memory. The meanings of thousands of everyday perceptions, the bases (51) the decisions we make, an d the roots of our habits and skills are to be (52) in our past experiences, which are brought into the present (53) memory.
Memory can be defined as the capacity to keep (54) available for later use. It includes not only "remembering" things like arithmetic or historical facts, but also any change in the way an animal typically behaves. Memory is (55) when a rat gives up eating grain because he has sniffed something suspicious in the grain pile. Memory is also involved when a six-year-old child learns to swing a baseball bat.
Memory (56) not only in humans and animals but also in some physical objects and machines. Computers, for example, contain devices for storing data for later use. It is interesting to compare the memory-storage capacity of a computer (57) that of a human being. The instant-access memory of a large computer may hold up to 100000 "words" —ready for (58) use. An average American teenager probably recognizes the meanings of about 100000 words of English. However, this is but a fraction of the total (59) of information which the teenager has stored. Consider, for example, the number of facts and places that the teenager can recognize on sight. The use of words is the basis of the advanced problem-solving intelligence of human beings. A large part of a person’s memory is in terms of words and (60) of words.
56()。
A. exists
B. appears
C. affects
D. seems