Slope Fields Question 1

Shown above is a slope field for which of the following differential equations?

\dfrac{dy}{dx}=\dfrac{x}{y}

\dfrac{dy}{dx}=xy

\dfrac{dy}{dx}=x+y

\dfrac{dy}{dx}=x-y

Approach

The slope is equal to 0 when the $x$ and $y$ value are equal and opposite. For example, the slope is 0 at $(-3,3)$ and $(2,-2)$

The only equation which works is $x+y$ .