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问题 单项选择题

设计工作位置时，必须充分考虑人员脚踏和站立的安全性。若操作人员经常变换工作位置，则必须在生产设备上配置安全走板。安全走板的宽度应不小于（）毫米，走板，梯子、平台均应具有良好的防滑性能

A.200

B.300

C.400

D.500

答案

参考答案：D

选择题

南水北调工程可能导致南方水系中的血吸虫随水北上，专家担心血吸虫会在北方水系中形成新的亚种或物种，对北方人民的健康形成新的威胁。假如南方的部分血吸虫来到北方，相关叙述错误的是[ ]

A．会慢慢形成新的种群

B．会因定向变异形成新的亚种或物种

C．可能与南方的血吸虫之间形成地理隔离

D．可能与南方的血吸虫之间形成生殖隔离
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单项选择题

The de facto standard Application Program Interface (API) for TCP/IP applications is the “sockets” interface. Although this API was developed for （71） in the early 1960s it has also been implemented on a wide variety of no-Unix systems. TCP/IP （72） Written using the sockets API have in the past enjoyed a high degree of portability and we would like the same （73） with IPv6 applications. But changes are required to the sockets API to support IPv6 and this memo describes these changes. These include a new socket address structure to carry IPv6 （74） ,new address conversion functions, and some new socket options. These extensions are designed to provide access to the basic IPv6 features requited by TCP and UDP applications, including multicasting, while introducing a minimums of change into the system and providing complete （75） for existing IPv4 applications.

A．availability 

B．compatibility 

C．capability 

D．reliability
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