Answer Description
Don't let the wording confuse you! You are looking for the option that is NOT described as non-volatile. Non-volatile memory retains data without a power source. Flash memory (like in thumb drives), SSD hard drives and tape drives do not require a power source to retain data. Random Access Memory (RAM) is volatile and loses it's data without a power source and is therefor not described as non-volatile.
Wikipedia
Non-volatile memory, nonvolatile memory, NVM or non-volatile storage is a type of computer memory that can retrieve stored information even after having been power cycled (turned off and back on). The opposite of non-volatile memory is volatile memory which needs constant power in order to prevent data from being erased. Examples of non-volatile memory include read-only memory, flash memory, ferroelectric RAM, most types of magnetic computer storage devices (e.g. hard disk drives, floppy disks, and …
Non-volatile memory - Wikipedia, the free encyclopedia