Explanation: The vertical amplifier directly processes and amplifies the incoming signal from the probe before it is applied to the oscilloscope's vertical deflection plates. The *bandwidth* of this amplifier dictates the highest frequency it can accurately amplify without significant attenuation or distortion. If a signal's frequency exceeds the amplifier's bandwidth, the oscilloscope will not be able to display it faithfully, or at all. Thus, it sets the upper limit on the oscilloscope's maximum frequency response. The time base and horizontal sweep determine the rate at which the electron beam sweeps horizontally across the screen, controlling the *time scale* or *sweep rate* of the display, not the maximum frequency the input signal can contain. The power supply provides the necessary operating voltages for all the oscilloscope's circuits but does not directly limit the signal's frequency handling capability.