Assertion: Transition metal ion forming octahedral complexes undergo $S{p}^3{d}^2$ or  $d^{2}S{p}^3$ hybridization
Reason:  Strong field ligands force the unpaired electrons of central metal ion to pair up causing $d^{2}S{p}^3$ hybridization where as weak field ligands do not affect electronic configuration of the metal ion undergoes in $S{p}^3{d}^2$ hybridization.