下列事例中，能够增大压强的是（） A．固定零件时，常要在_爱下问搜题

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问题选择题

下列事例中，能够增大压强的是（　　）

A．固定零件时，常要在螺母下面垫上一片比较大的垫圈

B．菜刀钝了磨一磨，使它锋利些

C．在坦克的轮子上安装履带

D．房屋的地基砌得比墙厚

答案

A、固定零件时，常要在螺母下面垫上一片比较大的垫圈，是在压力一定时，增大受力面积来减小压强，保护零件．不符合题意．

B、菜刀钝了磨一磨，是在压力一定时，减小受力面积来增大压强，使它锋利些．符合题意．

C、在坦克的轮子上安装履带，是在压力一定时，增大受力面积来减小压强，保护路面．不符合题意．

D、房屋的地基砌得比墙厚，是在压力一定时，增大受力面积来减小压强，保护地基．不符合题意．

故选B．

单项选择题

For nearly ten years, the Unified Modeling Language (UML) has been the industry standard for visualizing, specifying, constructing, and documenting the（71）of a software-intensive system. As the （72）standard modeling language, the UML facilitates communication and reduces confusion among project （73）. The recent standardization of UML 2.0 has further extended the language’s scope and viability. Its inherent expressiveness allows users to （74） everything from enterprise information systems and distributed Web-based applications to real-time embedded systems. The UML is not limited to modeling software. In fact, it is expressive enough to model （75）systems, such as workflow in the legal system, the structure and behavior of a patient healthcare system, software engineering in aircraft combat systems, and the design of hardware. To understand the UML, you need to form a conceptual model of the language, and this requires learning three major elements: the UML’s basic building blocks, the rules that dictate how those building blocks may be put together, and some common mechanisms that apply throughout the UML.

A．real

B．legal

C． de facto

D．illegal

填空题

FTP主要完成Internet上主机之间的______。