Which of the following is not the graph of a quadratic polynomial?

The shape of a quadratic polynomial is either upward or downward U - shaped curve i.e., an upward or downward parabola. Also, the graph of the quadratic equation cuts the X - axis at the most at two points, but in fig(D) it cuts the X - axis at three points.

∴ fig (D) is not the graph of a quadratic polynomial.