The correct option is C 14ε0
So the formula to find the potential at an axial point for a charged disk is,
V=2πσ[√r2+R2−r]4πε0
Where,σ is the charge density, R is the radius of the disk and r is the distance of the point from the center. If you don’t know where this formula came from, I encourage you to take a pen and a paper and derive it. It's very simple. Try it! Anyways, substituting in the values of corresponding variables we get,
V=2π×0.5[√32+42−4]4πε0V=14ε0