The largest data storage device in a computer is the hard disk.
The hard disk is a non-volatile storage device that is used to store and retrieve digital information. It is typically the largest storage device in a computer and is responsible for holding the operating system, software applications, and user data. Here are some key points to consider:
- Capacity: Hard disks have significantly higher storage capacities compared to other storage devices. They are available in various sizes, ranging from a few hundred gigabytes (GB) to several terabytes (TB) of storage space.
- Physical Structure: A hard disk consists of one or more spinning disks, known as platters, which are coated with a magnetic material. The platters are mounted on a spindle and rotate at high speeds. Data is stored on these platters in the form of magnetic patterns.
- Read and Write Operations: The hard disk uses read/write heads to access and modify data on the spinning platters. The heads move across the platters to read or write data by detecting the magnetic patterns.
- Speed: Hard disks have relatively slower access and data transfer speeds compared to other storage devices, such as solid-state drives (SSDs). This is because the read/write heads need to physically move to the correct location on the platters.
- Permanent Storage: Unlike volatile memory (RAM), the data stored on a hard disk is retained even when the computer is powered off. This makes it a suitable choice for long-term storage of files and applications.
- External Hard Drives: In addition to internal hard disks, there are also external hard drives that can be connected to a computer via USB or other interfaces. These provide additional storage space and can be easily transported.
In conclusion, the hard disk is the largest data storage device in a computer. It offers high storage capacity, permanent storage, and is responsible for holding the operating system and user data.

For most computers, the largest storage device is the hard drive or SSD. ... For example, over the evolution of the hard drive, their storage capacity has increased from 5 MB to several terabytes in size.
So, the correct answer is hard disk that is " B "