Which of the following best describes a prototype?

A prototype is best described as a full-scale model of a project for testing. This stage in the engineering design process allows designers and engineers to evaluate the functionality, design, and feasibility of their concepts in a tangible form. By creating a prototype, developers can experiment with materials, assess performance under real-world conditions, and gather user feedback, which is essential for refining the final product before it goes into full production.

The other options reflect different aspects of the engineering and design process. A finalized product ready for market indicates that the item has completed all stages of development and is now available for consumers; it is not representative of the iterative process that prototypes involve. A theoretical concept pertains to ideas or initial brainstorming stages and lacks the physical presence needed for testing. A visual presentation of designs through CAD focuses on the digital modeling aspect of design, rather than the hands-on, practical testing that a prototype offers.