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问题 多项选择题

按病因及发病机制进行贫血分类属于红细胞生成减少的有：（）

A.再生障碍性贫血

B.遗传性球形红细胞增多症

C.缺铁性贫血

D.蚕豆病

E.巨幼细胞性贫血

答案

参考答案：A, C, E

单项选择题

Both bus and tree topologies are characterized by the use of multipoint（）．For the bus，all stations attach，through appropriate hardware（）known as a tap，directly to a linear transmission medium，or bus．Full-duplex operation between the station and the tap allows data to be transmitted onto the bus and received from the（）．A transmission from any station propagates the length of the medium in both directions and can be received by all other（）．At each end of the bus is a（），which absorbs any signal，removing it from the bus．

Both bus and tree topologies are characterized by the use of multipoint（）．

A．medium

B．connection

C．token

D．resource
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问答题

一个计算机有Cache和一个用作虚拟内存的磁盘。若从Cache中读取一个字所用的时间为Ans，从内存中将一个字读入Cache的时间为Bns，从磁盘中将一个字调入内存的时间为Cns。若在Cache中读取一个字的命中率是(n-1)/n，在内存中读取一个字的命中率是(m-1)/m，则平均访问时间是多少
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