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 first step is（）.

A．use-case modeling

B．class modeling

C．dynamic modeling

D．behavioral modeling