The correct answer is D. Off-line.
An off-line device or system is not directly connected to the CPU. This means that it cannot be accessed or controlled by the CPU without first being connected to it. Off-line devices are often used for storage or backup purposes.
A keyboard is an input device that allows users to enter text into a computer. It is typically connected to the CPU via a USB cable.
Memory is a storage device that stores data and programs that are currently being used by the CPU. It is typically located on the motherboard of the computer.
On-line devices or systems are directly connected to the CPU. This means that they can be accessed and controlled by the CPU without first being connected to it. On-line devices are often used for input, output, or storage purposes.
None of the above is not a valid option.