N3−(Azide):Nˉ=N+=Nˉ↔Nˉ−N+≡N
It has sp hybridised central atom. Hence it is linear in shape.
I3−(triiodide):

It has linear geometry, sp3d hybridisation with three lone pairs at central atom.
NO2− (nitrite) : 
It is (nonlinear) bent shaped as it has sp2 hybridisation with one lone pair at central atom.
O3 (ozone) : 
It Is bent in shape with sp2 hybridisation and one lone pair at central atom.
SO2(sulphur dioxide) :

It is bent in shape with sp2 hybridisation and one lone pair at central atom.
So 3 among the given molecules is bent in shape.