Which of the following is not a magnetic disk ?

Hard Disk
Floppy Disk
Bernoulli Disk
CD – ROM

The correct answer is (d). CD-ROM is not a magnetic disk. It is an optical disk.

A magnetic disk is a data storage device that uses magnetic fields to store and retrieve digital information. The most common type of magnetic disk is the hard disk drive (HDD), which is a large, fixed-size disk that is typically installed inside a computer. Floppy disks are smaller, removable magnetic disks that were once widely used but are now obsolete. Bernoulli disks are a type of magnetic disk that was once used in high-end computers but is now also obsolete.

A CD-ROM (compact disc read-only memory) is a type of optical disc that can be read from but not written to. CD-ROMs are typically used to store software, music, and other data.