The correct options are
B HgCl2
D ZnI2
Isostructural chemical compounds have similar chemical structures.Compounds which are isoelectronic usually have similar chemical structures. both HgCl2, ZnI2(both are linear) have same number of valence electrons,so they are isostructural.
But SnCl2 and SCl2 have different structures due to the difference in their valence electrons.
Hence options B & D are correct.