A system's architecture is a representation of a system in which there is a mapping of（functionality）onto hardware and software components, a mapping of the（software architecture）onto the hardware architecture. and a concern for the human interaction with these components. That is, system architecture is concerned with a total system, including hardware. software, and humans. Software architectural structures can be divided into three major categories, depending on the broad nature of the elements they show. 1）（Module structures）embody decisions as a set of code or data units that have to be constructed or procured. 2）（Component-and-connector structures）embody decisions as to how the system is to be structured as set of elements that have runtime behavior and interactions. 3）（Allocation structures）embody decisions as to how the system will relate to non software structures in its environment(such as CPUs, file systems, networks, development teams, etc.).
系统架构是覆盖硬件、软件及人机交互的全系统抽象表达，核心包含两项关键映射：一是将系统整体功能拆解映射至对应软硬件组件，二是将软件架构适配映射到硬件架构，同时需兼顾人与系统各组件的交互设计。软件架构可划分为三大核心结构类别：模块结构属于静态代码层结构，以代码或数据单元为核心组织逻辑，明确系统静态模块的划分与依赖关系，为开发阶段的代码构建与管理提供支撑；构件-连接器结构聚焦运行时动态行为，描述系统在运行状态下的组件协作模式与交互路径，保障系统动态运行的稳定性与交互效率，像并发处理、组件通信这类动态场景都依赖该结构实现；分配结构则承担系统与非软件环境的衔接功能，既负责将系统组件分配匹配到CPU、网络等硬件资源，也涵盖开发任务到团队的分配逻辑，打通软件系统与物理环境、组织环境的关联通道。
本题考察的是系统架构与软件架构三种主要结构分类。
语境定位：原句为 “A system's architecture is a representation of a system in which there is a mapping of ____ onto hardware and software components, a mapping of the”。空前 which there is a mapping of；空后 onto hardware and software components a 是判断本空的关键。
答案判断：上下文强调的专业概念是“功能，指系统要提供的能力和服务”，该词能把前后语义自然衔接起来。因此应选 functionality。
选项辨析：
A. attributes：是质量属性，并非主要映射对象。
B. constraint：约束条件，不是核心映射。
C. functionality：功能，符合语境。
D. requirements：需求范围更大，不仅限于架构映射。
因此，选项 C 正确。