Which memory is nonvolatile and may be written only once?

Answer: Option C

PROM memory is non-volatile and may be written only once. A programmable read-only memory (PROM) or field programmable read-only memory (FPROM) or one-time programmable non-volatile memory (OTP NVM) is a form of digital memory where the setting of each bit is locked by a fuse or antifuse.