Chapter 13 - Section 13.1 - Functions of Several Variables - Exercises - Page 682: 34

$\bf{c}$

We can see that there is a peak erecting from the center of the xy-palne when we look at the graph of the 3D surface in $\bf{c}$. This matches the graph of the 2D level curves that has oval rings from the origin (0,0) of the xy plane. Hence, our correct option is $\bf{c}$.