To determine which among the given options can be considered a permanent memory of a computer, let's examine each option:

• Hard Disk: A hard disk is a type of storage device used to store data permanently. Its capacity to store data without the need for electricity makes it a form of non-volatile storage, meaning the data is retained even when the power is turned off. This characteristic defines it as a permanent memory of a computer.
• CPU (Central Processing Unit): The CPU is the brain of the computer where most calculations take place. It is responsible for executing instructions of a computer program. However, it is not used to store data permanently. Therefore, it is not considered permanent memory.
• RAM (Random Access Memory): RAM is a type of volatile memory, which means it loses its contents when the power is switched off. It is used for temporarily storing data that the CPU needs during execution. Due to its volatile nature, RAM is not a permanent memory.
• Motherboard: The motherboard is a main circuit board that holds and allows communication between many of the crucial electronic components of a system. It does not store any data permanently. Hence, it is not considered permanent memory.

Based on the explanations above, Hard Disk is the correct answer because it is a permanent storage device in a computer.