冷战后的世界并没有变成美国所希望的单极世界，发端于两极格局时期的国际政治多极化趋势正在继续发展。世界政治格局多极化趋势的根源是[ ]

A．霸权主义对世界和平的威胁

B．美苏对立的两极格局不复存在

C．世界力量对比出现了新变化

D．经济结构的多极化

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 determines 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