How can "actual reduction to practice" be demonstrated?

To demonstrate "actual reduction to practice," one must show that the invention has been physically made or practiced in a definitive form. This means that the invention has gone beyond just the theoretical stage or conceptualization and has been realized in a tangible form, either through constructing a prototype or by performing the method described in the invention. This kind of demonstration is pivotal in asserting that the invention works as intended and meets the requirements set for a patent.

Filing a provisional patent application, while a significant step in the patent process, does not constitute actual reduction to practice since it primarily serves to secure an early filing date and does not require a working model. Similarly, merely describing the invention in detail within a patent application or obtaining a foreign patent does not provide evidence that the invention has actually been constructed or successfully executed, which is the essence of "actual reduction to practice." Thus, constructing a prototype or performing the method effectively showcases that the invention has been realized in practice, which is why this choice is the correct demonstration of actual reduction to practice.