In requirements engineering, prototyping is primarily used to:

Concept

A software prototype is an early, partial model of a proposed system. Stakeholders interact with it before full-scale construction so that unclear, incomplete, or conflicting requirements can be elicited, validated, and refined.

Application

The stem asks for the primary purpose of prototyping. The option “refine and establish requirements during requirements gathering” directly expresses the feedback-driven requirements-elicitation role of a prototype.

Contrast

• “Test the software as an end product” refers to testing a completed or near-complete product, whereas a prototype is an early model.

• “Expand design details” concerns elaborating architecture or implementation specifications; that is not the central requirements-elicitation purpose asked here.

• “Eliminate the need for requirements documentation” would remove the agreed record of needs, constraints, and acceptance criteria; prototyping does not remove the need for that documentation.

Cross-check

If stakeholder feedback on the early model changes or clarifies what the system must do, the prototype has served requirements gathering before the final product is built.

Result

Therefore, prototyping is used to refine and establish requirements during requirements gathering.