"You ask... We explain"

1. Due to Nitrogen gas and oxygen gas being non polar molecules and since the intermolecular forces that exist are dispersion forces(weak) then they have low boiling points since they are easily broken.

2. H2O has hydrogen bonding, but H2S has London Dispersion Forces. Since hydrogen bonds are stronger intermolecular forces than London Dispersion Forces then they are harder to break making them have a higher boiling point than H2S.

3. When Sublimation occurs the molecules in the iodine solid experience much weaker intermolecular forces and as a result the particles a more spread out making it gaseous.