One of these is an impossible electrostatic field. Which one? Here k is a const...

One of these is an impossible electrostatic field. Which one?

Here k is a constant with the appropriate units. For the possible one, find the potential, using the origin as your reference point. Check your answer by computing ∇V. [Hint: You must select a specific path to integrate along. It doesn’t matter what path you choose, since the answer is path-independent, but you simply cannot integrate unless you have a definite path in mind.]