Tetraaquadiamminecobalt (II) chloride
Tetraaquadiamminecobalt (III) chloride
Diamminetetraaquacobalt (II) chloride
Diamminetetraaquacobalt (III) chloride
The IUPAC name of the complex given is Diamminetetraaquacobalt (III) chloride. The charge on central Co atom is +3. Hence, option (d) is correct.