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Object-oriented analysis (OOA) is a semiformal specification technique for the object-oriented paradigm. Object-oriented analysis consists of three steps. The first step is（）. It determines how the various results are computed by the product and presents this information in the form of a（） . and associated scenarios. The second is （）, which determines the classes and their attributes; Then determine the interrelationships and interaction among the classes. The last step is （）, which determines the actions performed by or to each class or subclass and presents this information in the form of（） .

The last step is （）.

A.use-case modeling

B.class modeling

C.dynamic modeling

D.behavioral modeling

真空吸尘系统三角的夹角不得大于（），四通制作应采用两个斜三通的做法。

A.40℃

B.45℃

C.50℃

D.55℃

应急发电机在运转时应要检查的内容？

何为脆性破坏的基本条件？

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