Correct Answer - A
`SCl_4` is not isostructural with `SiCl_4` because it shows square planar structure due to involvement of repulsion between lone pair and bond pair of electrons.
`SO_4^(2-)` shows tetrahedral structure due to `sp^3` hybridisation.
`PO_4^(3-)` shows tetrahedral structure due to `sp^3` hybridisation.
`NH_4^(+)` shows tetrahedral structure due to `sp^3` hybridisation.