The correct answer is D. diskettes.
A removable disk is a data storage device that can be removed from a computer and stored elsewhere. Removable disks include floppy disks, Zip disks, and USB flash drives.
A fixed disk is a data storage device that is permanently installed in a computer. Fixed disks are also known as hard disks or hard drives.
A mass storage system is a data storage device that can store a large amount of data. Mass storage systems include tape drives, optical drives, and solid-state drives.
Diskettes are a type of removable disk that was once commonly used to store data. However, diskettes have been largely replaced by other types of removable disks, such as USB flash drives.