Answer:
B, Resolution
Step-by-step explanation:
-Keystone is a function that enables to change the image from the source to create a rectangular image.
-Resolution is the number of pixels that can be seen in a screen. The size of an image depends on the resolution and the size of the monitor.
-Privacy filter is an effect that makes it hard for someone to see the screen if he/she is not in front of it.
-Frame rate is the speed at which still images appear on a screen.
According to this, the setting that the technician should modify is the resolution.