Which of the following best describes a prototype?

A prototype is best described as the beginning of a design or layout before mass production. This definition captures the essence of what a prototype is meant to be: a preliminary model that allows designers, engineers, and stakeholders to test concepts, functionalities, and aesthetics before committing to final production. Prototypes can take various forms, such as sketches, 3D models, or other representations, enabling the exploration of ideas, identification of potential issues, and gathering of feedback that informs the development process.

In contrast, the other options imply a more advanced stage of product development or unrelated concepts. A completed product ready for mass production signifies that a design has been finalized and is ready for market, which an early-stage prototype is not. Similarly, the final version of a layout indicates that all iterations and revisions are complete, which also does not reflect the prototype's purpose of testing initial ideas. Lastly, a marketing strategy focuses on how to promote and engage with an audience, which is a different area of expertise entirely from the design and development phase represented by a prototype.