Which of the following species contain(s) an S-S bond?

Thiosulphate $\mathrm{S}{}_2\mathrm{O}{}_3{}^{2-}$ is $\mathrm{S}-\mathrm{SO}{}_3{}^{2-}$, dithionite is ${}_{}^{}{}_{}^{-}\mathrm{O}{}_2\mathrm{S}-\mathrm{SO}{}_2{}^{-}$ and dithionic acid has an S-S bond. Pyrosulphuric acid (oleum) has two S atoms linked through an oxygen bridge, S-O-S, and no S-S bond.