Each quarter of a vessel of depth `H` is filled with liquids of the refractive indices `n_(1),n_(2), n_(3)` and `n_(4)` from the bottom respectively. The apparent depth of the vessel when looked normally is
A. `(H(n_(1)+n_(2)+n_(3)+n_(4)))/(4)`
B. `(H(1/n_(1)+1/n_(2)+1/n_(3)+1/n_(4)))/(4)`
C. `((n_(1)+n_(2)+n_(3)+n_(4)))/(4H)`
D. `(H(1/n_(1)+1/n_(2)+1/n_(3)+1/n_(4)))/(2)`