Which of the following is a data storage device?

A hard drive is a data storage device that is used to store and retrieve digital information on a computer. It can hold the operating system, software applications, and various files such as documents, images, and videos. Hard drives may be either in the form of traditional spinning disks (HDDs) or solid-state drives (SSDs), which use flash memory to store data.

The function of a hard drive is to provide long-term storage for data, which persists even when the computer is powered off. This is distinct from RAM, which is memory used for temporary storage while a computer is running and does not retain data after the power is turned off. A Network Interface Card connects a computer to a network but does not store data itself. A Power Supply provides electrical power to the computer's components, without storing any data. Thus, the hard drive is correctly identified as the primary data storage device among the choices provided.