Explanation:

- CD-ROM is a type of secondary memory.

- Correct Answer: Option 1 - secondary memory

- It is a non-volatile storage used to store data and programs permanently.

- It uses optical technology for reading and writing data.

- Magnetic memory:

- Refers to storage devices like hard drives and magnetic tapes.

- They use magnetic methods to write and retrieve data.

- Memory register:

- It's a small, fast storage location within the CPU.

- Used to hold data temporarily during processing.

- Semiconductor memory:

- Includes RAM, ROM, and flash memory.

- It is used for both temporary and permanent storage based on type.