A requirement is simply a statement of what the system must do or what characteristics it needs to have. Requirements written from the perspective of user and focus on user needs are called (1). Requirements written from the developer's perspective and describe how the system will be implemented are called (2). Requirements evolve from detailed statements of the business capabilities that a system should have to detailed statements of the technical way in wluch the capabilities will be implemented in the new system. Requirements can be either functional or nonfunctional in nature. For example, during the analysis phase of travel vehicles sales system, the system that must have the ability to search for available inventory is (3). The requirement that the system should be able to work on any Web browser belongs to (4). That customer personal information is protected in compliance with the Data Protection Act is a requirement of (5).
空白（3）处应选择（）
A.a functional requirement
B.a technical requirement
C.a noperational requirement
D.a service requirement