操作"患者坐位，小腿垂于治疗床沿。治疗者面向患者坐在一矮凳上，双手握住小腿近端稍向下牵引。内旋时，双手向内转动小腿，外旋时，向外转动小腿"属于（）

A.长轴牵引膝关节

B.旋转摆动膝关节

C.伸膝摆动膝关节

D.前后向滑动膝关节

E.后前向滑动膝关节

(74) is NOT served by building a prototype.

A．It takes the place of the final system

B．It is used as the foundation of the larger projects

C．It assists in estimating the cost of the project

D．It assists in gathering software requirements