The boiling points of the hydrogen halides are $\mathrm{HF}$ $293\mathrm{K}$, $\mathrm{HCl}$ $188\mathrm{K}$, $\mathrm{HBr}$ $207\mathrm{K}$ and $\mathrm{HI}$ $237\mathrm{K}$, although the dipole moment decreases from $\mathrm{HCl}$ to $\mathrm{HI}$. The best explanation is that

1. A$\mathrm{HF}$ is hydrogen bonded, and from $\mathrm{HCl}$ to $\mathrm{HI}$ increasing dispersion forces outweigh the decreasing dipole-dipole forces
2. B$\mathrm{HI}$ is more ionic than $\mathrm{HCl}$
3. Call hydrogen halides are hydrogen bonded to the same extent
4. Ddipole-dipole forces increase from $\mathrm{HCl}$ to $\mathrm{HI}$