Balance the charges on the complex ion. The two $en$ ligands are neutral and contribute $0$; the two $Cl^{-}$ contribute $2\times(-1)=-2$. Writing the metal oxidation state as $n$ and equating to the ionic charge $+2$: \[n+(-2)=+2 \;\Rightarrow\; n=+4\]So platinum is in the $+4$ state. Correct option: (B) +4.