Ravi,like many project__(1)__,had studied the waterfall model of software development as the primary software life-cycle__(2)__.He was all set to use it for an upcoming project,his first assignment.However,Ravi found that the waterfall model could not be used because the customer wanted the software delivered in stages,something that implied that the system had to be delivered and built in__(3)__and not as__(4)__. 　

The situation in many other projects is not very different.The real world rarely presents a problem in which a standard process,or the process used in a previous project,is the best choice.To be the most suitable,an existing process must be__(5)__to the new problem.

A development process,even after tailoring,generally cannot handle change requests.To accommodate change requests without losing control of the project,you must supplement the development process with a requirement change management process.

空白（3）处应选择（）

A.parts

B.modules

C.software

D.awhole

试析建国以来社会保障制度的成就与问题。