An input/output device at which data enters or leaves a computer system is

Answer: Option B

The correct answer is B: Terminal.
Let's break down why:

* What is an Input/Output (I/O) Device? I/O devices are how we, as users, interact with a computer. They allow us to give the computer instructions (input) and for the computer to show us results (output).

* Option A: Keyboard A keyboard is primarily an input device. We use it to type data *into* the computer. It doesn't generally *display* information *from* the computer.

* Option B: Terminal A terminal is a device that combines both input and output capabilities. It typically includes a display screen (output) and a keyboard (input), allowing for two-way communication with the computer system. It acts as an interface to access the computer.

* Option C: Printer A printer is primarily an output device. It takes data *from* the computer and prints it on paper. It doesn't usually allow us to give instructions *to* the computer.

* Option D: Plotter A plotter is another type of output device, similar to a printer, but typically used for larger-format graphics. It also doesn't generally receive instructions from a user.

* Option E: None of the above Since a terminal *is* an I/O device, this option is incorrect.

In summary: A terminal allows data to both *enter* (input - via keyboard) and *leave* (output - via the screen) the computer system, making it the most fitting answer.