There are four ____________ on the floor .      [ ]

A. pair of red shoes          

B. pairs of red shoe      

C. pairs of red shoes          

D. pair of red shoe

（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 process concerns into constructs called objects.

（74）处填（）。

A．PERT

B．DFD

C．ERD

D．UML