Explanation:

When software is made available in the market for users, it is typically distributed as a **software package**. A software package refers to a collection of programs, libraries, data, and documentation that are bundled together and sold or distributed as a single unit to perform specific tasks or provide a set of functionalities. While it is indeed a 'software program' (option a), 'software package' (option b) is a more specific and appropriate term for a commercial product. 'Software system' (option c) is a broader term that can refer to an entire collection of integrated software components, including operating systems and applications, but 'package' is more suitable for a marketable product. 'Software language' (option d) refers to programming languages, not the end-user product itself. Therefore, 'software package' accurately describes a marketable program.