A coordination complex of type MX2Y2 (*M*-metal ion; *X*, *Y*-monodentate ligands), can have either a tetrahedral or a square planar geometry. The maximum number of possible isomers in these two cases are respectively :
(1) 1 and 2
(2) 2 and 1
(3) 1 and 3
(4) 3 and 2