d
\(\left( A \right)\,N{a_4}\left[ {\mathop F\limits^x e{{\left( {CN} \right)}_5}\left( {NOS} \right)} \right]\)

\((+1) 4+x+(-1) 5+(-1) 1=0\)

\(x=+2\)

\(\left( B \right)\,N{a_4}\left[ {\mathop {Fe{O_4}}\limits^y } \right]\)

\((+1) 4+y+(-2) 4=0\)

\(y=+4\)

\(\left( C \right)\,\left[ {F\mathop {{e_2}}\limits^z {{\left( {CO} \right)}_9}} \right]\)

\(2 z+0 \times 9=0\)

\(z=0\)

so \(( x + y + z )=+2+4+0\)

\(=6\)