\(In\) the face-centred cubic lattice structure of gold the closest distance between gold atoms is ('a' being the edge ength of the cubic unit cell)
(A) \(a \sqrt{2}\)
(B) \(\frac{a}{\sqrt{2}}\)
(C) \(\frac{a}{2 \sqrt{2}}\)
(D) \(2 \sqrt{2} \mathrm{a}\)