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问题 单项选择题

右心房、右心室、肺循环、左心房血流增多，而左心室、体循环血流量减少，这是下述哪一种先心病的血液动力学改变（）

A.动脉导管未闭

B.室间隔缺损

C.肺动脉狭窄

D.法洛四联症

E.房间隔缺损

答案

参考答案：E

单项选择题

The network layer provides services to the transport layer. It can be based on either（71）. In both cases，its main job is （72） packets from the source to the destination. In network layer，subnets can easily become congested，increasing the delay and（73）for packets. Network designers attempt to avoid congestion by proper desing,Techniques include （74） policy，caching，flow control，and more. The next step beyond just dealing with congestion is to actually try to achieve a promised quality of service. The methods that can be used for this include buffering at the client，traffic shaping，resource（75），and admission control. Approaches that have been designed for good quality of service include integrated services (including RSVP), differentiatd services, and MPLS.

空白处（73）应选择（）

A．lowering the throughput

B．lowering the correctness

C．lowering the effectiveness

D．lowering the preciseness
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选择题

二氧化硫的催化氧化是放热反应。下列关于接触法制硫酸的叙述中正确的是 

A．为提高SO2的转化率，接触室内反应温度选定在400℃~500℃

B．为防止催化剂中毒，炉气在进入接触室之前需要净化

C．为防止污染大气，从吸收塔出来的尾气常用NaOH溶液吸收

D．为提高SO3的吸收效率，用稀硫酸代替水吸收SO3　.
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