What is a light pen?
A.A mechanical input device.
B.Optical input device.
C.Electronic input device.
D.Optical output device.

Hint: We know that the input is discrete or continuous and by the discrete it means that the keys have to be pressed. On the other hand, an example of consciousness can be the position of the mouse. Though, one should note that the mouse digitizes into a discrete quantity.

Complete answer:
As we know, the optical mouse uses optical electronics. This is done to track the movement and is also more reliable than a mechanical mouse. It also requires less maintenance. However, the performance of this mouse is affected by the surface on which the mouse is used. For best results, a plain and non-glossy mouse mat should be used for this mouse. Similarly, this is a device similar to a pen. A light pen is used for selecting a displayed menu item or for drawing pictures on the monitor screen. There is a photocell and an optical system present within a small tube. The tip of a light pen is moved over a monitor screen.
Also, the light pen is an optical input device. This device is designed to point at and shoot at targets on the screen in an arcade or a video game. A light gun was also used for the first time on the MIT Whirlwind computer. The device works by pointing it at a target on the screen. After that, the trigger can be pulled, and the screen would go blank for a fraction of a second. During this second, the photodiode, which is present in the barrel, determines where the gun is pointed. For example, ducks can be shot in a duck hunting game with this device.

Therefore, the correct answer is option B.

Note:
Remember that the modality of input. It can include audio, visual or mechanical motion. The number of degrees of freedom that is involved. For example, the traditional two-dimensional mouse or the three-dimensional navigators are designed for CAD applications specifically.