Which one of the following nitrogen oxides may dimerize?

Nitrogen dioxide (NO₂) is a paramagnetic molecule with an unpaired electron on the nitrogen atom. Due to this unpaired electron, two NO₂ molecules can pair up to form dinitrogen tetroxide (N₂O₄), which is a diamagnetic dimer. This dimerization equilibrium (2NO₂ ⇌ N₂O₄) is well-known and is temperature-dependent. N₂O (nitrous oxide), N₂O₃ (dinitrogen trioxide), and N₂O₅ (dinitrogen pentoxide) are already even-electron species or dimers themselves and do not undergo simple dimerization like NO₂.