What must an inventor demonstrate to receive a utility patent?

To receive a utility patent, an inventor must demonstrate that the invention is functional and concrete. This means that the invention must provide a specific and practical utility or application. The patent law requires that the invention must be a process, machine, manufacture, or composition of matter that offers some identifiable benefit or effect. It cannot be merely an abstract idea or concept; it must have a tangible application, meaning it should be able to work and produce useful results.

The focus on functional utility aligns with the fundamental purpose of utility patents, which is to promote the progress of science and the useful arts by protecting inventions that offer new and beneficial ways to solve problems or provide utility. Thus, demonstrating that an invention is functional and has practical utility is essential for patent grant, making this option the correct answer.