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问题 单项选择题

1岁婴儿，阵发性哭闹，呕吐12小时，黏液血便1次。查体：体温37．8℃，精神差，明显腹胀，右下腹可触及肿物，压痛（+），最可能的诊断是（）

A.小儿急性阑尾炎

B.先天性巨结肠

C.胃肠炎

D.急性肠套叠

E.肠系膜淋巴结炎

答案

参考答案：D

选择题

大约在70个表型正常的人中有一个白化基因杂合子。一个表型正常、其双亲也正常、但有一个白化弟弟的女子与一无亲缘关系的正常男子婚配。他们的孩子患白化病的概率是多少？ [ ]

A．1/40

B．1/280

C．1/420

D．1/560

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单项选择题

Networks can be interconnected by different devices. In the physical layer, networks can be connected by (11) or hubs, which just move the bits from one network to an identical network. One layer up we find bridges and switches, which operate at data link layer. They can accept (12) ,examine the MAC address, and forward the frames to a different network while doing minor protocol translation in the process. In the network layer, we have routers that can connect two networks. If two networks have (13) network layer, the router may be able to translate between the packer formats. In the transport layer we find transport gateway, which can interface between two transport connections. Finally, in the application layer, application gateways translate message (14) . As an example, gateways between Internet e-mail and X.400 e-mail must (15) the e-mail message and change various header fields.

13（）

A.special

B.dependent

C.similar

D.dissimilar
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