（71） analysis emphasizes the drawing of pictorial system models to document and validate both existing and/or proposed systems. Ultimately, the system models become the（72）for designing and constructing an improved system. （73） is such a technique. The emphasis in this technique is process-centered. Systems analysts draw a series of process models called（74） . （75） is another such technique that integrates data and processConcerns into constructs called objects.

A．PERT

B．DFD

C．ERD

D．UML

下列哪一种文件存储设备不支持文件的随机存取

A．磁盘

B．光盘

C．软盘

D．磁带