Which modulation type primarily focuses on altering the route of an electron beam in CRT technology?

Deflection modulation is the correct answer because it involves changing the path of the electron beam in a cathode-ray tube (CRT). In CRT technology, the electron beam must be precisely controlled to accurately render images on the screen. This is accomplished through electromagnetic or electrostatic deflection systems that alter the trajectory of the beam, allowing it to hit specific points on the screen. By adjusting the strength and direction of the fields applied to the electron beam, the image can be scanned horizontally and vertically.

The other options refer to different aspects of image display in CRTs. Intensity modulation refers to varying the brightness of the pixels by changing the current in the electron beam itself. Color modulation deals with how the RGB components are mixed to produce various colors on the screen. Brightness modulation similarly focuses on the intensity of the light output. None of these methods directly involve altering the route or path of the electron beam, which is the primary focus of deflection modulation.