Sodium pentacyanonitrosylferrate(II) contains the complex ion with five $\mathrm{CN}{}^{-}$, one nitrosyl taken as $\mathrm{NO}{}^{+}$, and iron in the $+2$ state. Which is its formula?

1. A$\mathrm{Na}{}_3[\mathrm{Fe}(\mathrm{CN}){}_5\mathrm{NO}]$
2. B$\mathrm{Na}[\mathrm{Fe}(\mathrm{CN}){}_5\mathrm{NO}]$
3. C$\mathrm{Na}{}_2[\mathrm{Fe}(\mathrm{CN}){}_5\mathrm{NO}]$
4. D$\mathrm{Na}{}_4[\mathrm{Fe}(\mathrm{CN}){}_5\mathrm{NO}]$