The graph of a polynomial y = f(x) is shown in figure below, then the number of its zeros is: [Figure: Graph of y = f(x) on x-y axes. The curve starts below the x-axis at the far left, rises and crosses the x-axis, reaches a peak above the axis, falls and crosses the x-axis again, forms a flat trough below the axis (passing below the origin), then rises and crosses the x-axis a third time on the right.]