[Co(NH3)6]Cl3
[Pt(NH3)2Cl2]
[Co(NH3)4Cl2]
[Co(NH3)5Cl]Cl2
Homoleptic complexes are compounds in which all the ligands bound to the metal center are identical. Homoleptic complexes have only one type of ligand. So option A, [Co(NH3)6]Cl3, has the same ammonia ligand throughout.