Explanation: A video amplifier's purpose is to boost the video signal to a level suitable for driving a display device (like a CRT or LCD). The signals controlling the display's appearance are either direct inputs to the amplifier or control its operation. * **Contrast** controls the gain of the video amplifier. Increasing contrast increases the difference between the light and dark parts of the image by amplifying the video signal's amplitude swing. * **Brilliance** (or Brightness) controls the overall light output of the display. This is typically achieved by adjusting a DC offset level applied to the video signal, which is then amplified, setting the baseline brightness. * **Range**, especially in display systems like radar or oscilloscopes, refers to the sensitivity or scaling of the input signal. A "range" control effectively sets the amplitude of the input signal presented to the video amplifier for processing and display. Since all three directly affect the characteristics of the signal that the video amplifier processes, or the way the amplifier processes it, they are considered inputs to the video amplifier's functionality.