If the potential in a region is given by $V(x,y,z)=xy-3z-2,$ then the $y$ component of the

electric field in that region is

A$)x+y-6z-3.$

B$)-x.$

C$)-y.$

D$)x+y.$

So I know that the answer is B$)-$x$,$ but can an expert please give an in depth explanation of how we get there with the equations? And conceptually explain why this answer makes sense$/$why we use the equations we do to get this answer. Thank you.