Which of the following statements are correct?
I. The increasing order of covalent character of NaCl, RbCl, MgCl$_2$ is RbCl < NaCl <\ MgCl$_2$
II. The high boiling point of water is due to intramolecular hydrogen bonding
III. H$_2$O has more dipole moment among NH$_3$, H$_2$O, and HF