The correct answer is D. Mouse.
A DVD is a digital versatile disc, a type of optical disc storage medium. DVDs were initially developed to store and play video content, but are now also widely used for data storage.
A hard disk is a data storage device that uses magnetic storage to store and retrieve digital information. Hard disks are typically used in computers to store operating systems, applications, and user data.
A floppy disk is a removable magnetic storage medium that was used to store and transport data. Floppy disks were once the most common type of data storage device, but have been largely replaced by other storage media, such as USB drives and CDs.
A mouse is a pointing device that is used to control the cursor on a computer screen. Mice are typically connected to computers via a USB cable, but wireless mice are also available.
Of the above options, only a mouse is not a storage device.