The correct answer is D. 0.
A switch is a device that can be turned on or off. When a switch is turned on, it completes an electrical circuit and allows current to flow. When a switch is turned off, it breaks the electrical circuit and prevents current from flowing.
In a computer, each switch is represented by a binary number. A binary number is a number that is made up of only two digits: 0 and 1. The number 0 represents the OFF state of a switch, and the number 1 represents the ON state of a switch.
Therefore, the number that is represented by the OFF state of a switch is 0.