Memory in a computer system is required for storage and retrieval of the instructions and data. A system uses a variety of devices for storing these instructions and data that are required for its operation. The following two kinds of memory systems:Primary (main) Memory: Primary memories are used mainly for primary storage. It stores programs and data which are currently needed by the CPU. The primary memory is a static device. There is no rotating part in it. Examples include RAM, ROM, etc. Secondary Memory: It is the storage that the CPU cannot access directly. it's content firstly needs to be copied into ram and then transferred to CPU. It stores data that can be easily retrieved only by the main memory and used by the processor. Example, hard disk. Difference between Primary and Secondary memory:Primary memorySecondary memoryPrimary memory is temporary. Secondary memory is permanent. Primary memory is directly accessible by Processor/CPU. Secondary memory is not directly accessible by the CPU. Nature of Parts of Primary memory varies, RAM- volatile in nature. ROM- Non-volatile. Its always Non-volatile in nature. Primary storage is faster, more expensive, and persistent. Secondary memory devices are less expensive, slower when compared to primary memory devices. The memory devices used for primary memory are semiconductor memories. The secondary memory devices are magnetic and optical memories. Primary memory is also known as Main memory or Internal memory. Secondary memory is also known as External memory or Auxiliary memory. Examples: RAM, ROM, Cache memory, PROM, EPROM, Registers, etc. Examples: Hard Disk, Floppy Disk, Magnetic Tapes, etc. Therefore, option 2 is the correct answer.