Chapter 5 - Section 5.1 - Introduction to Polynomials and Polynomial Functions - Exercise Set - Page 324: 23

Not a Graph of a polynomial function.

The shape of graphs will be smooth and continuous for those polynomials of degree $2$ and higher than degree $2$. As we can see from the given graph that it does not represent a smooth and continuous shape but having sharp corner therefore it is Not a Graph of a polynomial function.