Which of the following is a secondary memory device?

The correct answer is B. Disk.

A secondary memory device is a storage device that is not directly accessible by the CPU. This means that data stored on a secondary memory device must be first transferred to the main memory before it can be processed by the CPU. Secondary memory devices are typically used to store large amounts

of data, such as programs, files, and user settings.

The keyboard is an

input device that is used to enter text into a computer. The ALU is the arithmetic and logic unit, which is a part of the CPU that performs arithmetic and logical operations.

Therefore, the only option that is a secondary memory device is B. Disk.