To solve this question, the user needs to know the differences between the types of computer memory.

A. CPU (Central Processing Unit) is not a type of memory, it is a processing unit that performs most of the processing inside a computer.

B. ROM (Read-Only Memory) is a type of non-volatile memory that retains its data even when the power is turned off. It is used to store firmware, BIOS, and other permanent system data.

C. RAM (Random Access Memory) is a type of volatile memory that does not retain its data when the power is turned off. It is used to temporarily store data while the computer is running.

D. DRAM (Dynamic Random Access Memory) is a type of volatile memory that requires constant refreshing to retain its data. It is used as the main memory in most computers.

E. DIMM (Dual In-Line Memory Module) is not a type of memory, it is a form factor for RAM modules.

Therefore, the correct answer is B. ROM.