Final answer:
An EPROM must be exposed to ultraviolet (UV) light in order to erase its stored data.
Step-by-step explanation:
An EPROM (Erasable Programmable Read-Only Memory) stores data using electrical charges trapped in floating gate transistors. In order to erase its stored data, an EPROM must be exposed to ultraviolet (UV) light. The UV light is used to remove the trapped electrical charges from the floating gate transistors, effectively resetting the memory.