Which of the following shapes is NOT associated with fluorescent lamps?

Fluorescent lamps are commonly available in several shapes, each designed for specific applications. The circular shape is typical for compact fluorescent lamps (CFLs), which are designed to replace traditional incandescent bulbs while fitting into standard light fixtures. The linear shape corresponds to the long, tube-like fluorescent bulbs that are prevalent in commercial and industrial lighting. U-shaped fluorescent lamps are also common and can fit in fixtures designed for specific applications.

In contrast, star-shaped fluorescent lamps are not standard or widely recognized in the industry. While creative designs and specialty lamps may exist, they are not typical shapes associated with fluorescent technology, which is focused on efficiency and functionality. Thus, this option stands out as one that is not associated with the typical offerings within fluorescent lamp designs.