单选题
System analysis is traditionally done top-down using structured analysis based on______(1)．Object-oriented analysis focuses on creation of models．The three types of the analysis model are______(2)．There are two substages ofobject-oriented analysis．______(3)focuses on real-world things whose semantics the application captures．The object constructed in the requirement analysis shows the______(4) of the real-world system and organizes it into workable pieces．______(5)addresses the computer aspects of the application that are visible to users．The objects are those which Call be expected to vary from time to time quite rapidly．