NH3 is neutral, making the first complex positively charged overall. Cl has a −1 charge, making the second complex the anion and so platinum ends with -ate.
Therefore, the complex with NH3 comes first, followed by the one with Cl.
Option (A) is correct. The I.U.P.A.C name for [Pt(NH3)4][PtCl4]
is tetraammineplatinum(II) tetrachloridoplatinate(II)