1. The problem asks to determine the amplitude of a sinusoidal graph. 2. The amplitude of a sinusoidal function is the distance from the centerline (midline) to a peak (maximum) or trough (minimum). 3. Given the graph has peaks at $y=4$ and troughs at $y=0$, and the centerline is at $y=2$. 4. The amplitude $A$ is calculated as the difference between the peak and the centerline: $$A = 4 - 2 = 2$$ 5. Alternatively, the amplitude can be found by half the distance between the peak and trough: $$A = \frac{4 - 0}{2} = 2$$ 6. Therefore, the amplitude of the sinusoidal graph is $2$.