The correct option is A 4k5
So what is the formula to find potential a point r distance away from a charge Q?
V=kQr
But here in this question instead of giving r, we are given that the point is at (3,4,0) and charge Q=4C is at origin (0,0,0).
So to get r, we use distance formula.
r=√(3−0)2+(4−0)2+(0−0)2
r=√25
r = 5
Now,
At (3,4,0), V=k×45
V=4k5
And potential is a scalar. Not a vector. So there can be no along with it.