If D Is Distance Between Centres of Two Parallel Track $\sqrt{1+N^2}$

If D is distance between centres of two parallel track of gauge G, then, total length of cross-over (from the point of commencement to the point of termination) with an intermediate straight portion and N crossing, is given by

A) DN + G [N + $\sqrt{1+N^2}$ ) ]
B) DN + G [2N + $\sqrt{1+N^2}$ ) ]
C) DN + G [3N + $\sqrt{1+N^2}$ ]
D) DN + G [4N + $\sqrt{1+N^2}$ ]