Which doesn't belong to the group?

To find which item does not belong to a group, look for the shared characteristic among most of the items and then identify the one that breaks that pattern.

A flash drive, a floppy disk, and a compact disk are all specific, physical secondary storage devices used to hold data outside the computer's main memory; they are portable, removable media that a user can carry, insert, and remove from a computer. A memory unit, by contrast, is a general term for the internal component of a computer responsible for storing data and instructions during processing (including RAM and the CPU's internal storage), not a specific portable storage device that you insert and remove.

Because flash drives, floppy disks, and compact disks are all concrete examples of a particular category of removable storage media, while "memory unit" describes the broader internal storage component of a computer as a whole, the memory unit is the one that does not belong to the group of portable storage devices.

Exam reminder: when grouping computer terms, distinguish between specific named devices (like a flash drive or compact disk) and general system components (like the memory unit), since the latter is a category, not an individual portable device.