Final answer:
System software acts as an intermediary layer between hardware and application software, which makes D the correct answer to the question. Software developers work in the quaternary sector of the economy. The mind and software are both seen as computation systems, paralleling the functions of the brain and hardware respectively.
Step-by-step explanation:
System software is the layer between the hardware and the application software. Therefore, the correct answer is D. System software serves as a foundation for application software and facilitates operations such as input/output processing, hardware management, and data storage, thus acting as an intermediary between the computer's hardware and the user-level software that performs specific tasks.
In the economic sectors, a software developer would be categorized in the quaternary sector, which deals with knowledge-based activities, such as information technology and software development. This places them into option D. Finally, the analogy that the mind is to the brain as software is to hardware reflects the conceptual parallel between cognitive functions and computer processes, where both carry out computations, albeit in vastly different substrates and complexities.