What does the system unit do?

The system unit is a crucial component of a computer that houses the primary devices necessary for its core operations. This includes the central processing unit (CPU), memory (RAM), and other critical components such as the motherboard and power supply. These elements work together to process data, perform calculations, and execute instructions provided by software applications.

The other options do not accurately capture the role of the system unit. While it does facilitate the interaction between software applications and hardware, it does not specifically store all software applications; that is typically done on storage devices like hard drives or SSDs. Providing a user interface for input is generally the role of peripherals like keyboards and mice, while the system unit serves as the central hub for processes. Lastly, the connection to external devices, like printers or monitors, is indeed a function of the system unit but does not fully represent its primary role, which is to house and manage the key operational components of the computer. Thus, identifying the system unit as the housing for primary devices offers a clearer, more precise understanding of its essential function within a computer system.