Final answer:
In BPMN, a task within a business process is best classified as a BPMN activity, which represents a single unit of work executed as part of the process flow.
Step-by-step explanation:
A task in a business process, within the context of Business Process Model and Notation (BPMN), is best represented by a BPMN activity. This is because BPMN activities encompass a variety of actions that can take place within a process, including tasks. A task is a fundamental work element that is executed as part of a process.
In BPMN, tasks are depicted as rectangles with rounded corners and represent a single unit of work, whereas BPMN flow objects like events and gateways have different shapes and serve different purposes. Events are represented by circles and denote something that happens, affecting the flow of the process. Gateways, shown as diamonds, are used to control the divergence and convergence of the flow in the process, and the BPMN flows, shown as arrows, illustrate the sequence in which activities occur.