Answer: NO2.
You can predict that two atoms with similar electronegativity will form covalent compounds while atoms with pretty different electronegativity will form ionic compounds.
Given that N and O are neighbors on the periodic table, you can predict they have similar electronegativities.
Also you can predict that from the fact that N and O are nonmetals, which also means that they will form covalent compounds.
The other compounds liste are formed by metals and non metals wich is an indication that they will have, at least, some ionic character.
Ergo, N and O will form covalent compounds, in this case NO2.
