d
The $IUPAC$ name of $K _2\left[ Cr ( CN )_2 O _2\left( O _2\right) NH _3\right]$ is Potassium amminedicyanodioxoperoxo chromate $(VI)$.The cation is potassium and the anion is the complex ion containing chromium metal in $+6$ oxidation state.
The oxidation state is written in roman numerals inside parenthesis.
The ligands $O$ and $O _2$ are oxo and peroxo respectively.
The prefix di indicates two.