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问题 计算题

人急行的速度大约是2m/s，人急行横过6m宽的马路需要的时间大约是多少秒？汽车的行驶速度如果是10m/s，人至少要在距行驶过来的汽车多少米处开始穿越马路？

答案

3s；30m

单项选择题

For（）service, we need a virtual-circuit subnet. Let us see how that works. The idea behind virtual circuits is to avoid having to choose a new（）for every packet sent. Instead, when a connection is established, a route from the（）machine to the destination machine is chosen as part of the connection setup and stored in tables inside the（）That route is used for all traffic flowing over the connection, exactly the same way that the telephone system works. When the connection is released, the virtual circuit is also terminated. With connection-oriented service, each packet carries an（）telling which virtual circuit it belongs to.

For（）service, we need a virtual-circuit subnet.

A．connectionless

B．connection-oriented

C．datagram

D．telegram
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单项选择题 案例分析题

男性，72岁，夜间睡眠中突感心前区疼痛，持续半小时不缓解，继之出现呼吸困难，不能平卧。

心电图：ST段V1-3弓背向上抬高，有宽而深的Q波，提示（）

A.急性心内膜下心肌梗塞

B.急性前壁心肌梗塞

C.急性广泛前壁心肌梗塞

D.急性高侧壁心肌梗塞

E.急性前间壁心肌梗塞
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