Which of the following is not considered an optical storage device?

Optical storage devices use lasers to read and write data on the medium, which is usually a reflective disc. CDs, DVDs, and Blu-ray discs all fall under this category, utilizing different technologies and capacities but fundamentally relying on optical methods for data storage and retrieval.

In contrast, a flash drive is a type of solid-state storage device that uses flash memory to store data, which is accessed electronically rather than optically. Flash drives are characterized by their speed, portability, and durability, and they do not require a laser to read or write data. This distinction makes the flash drive the only option listed that is not an optical storage device.