The main interactions between molecules of hydrogen chloride are examples of

            The main interactions between molecules of hydrogen chloride are examples of Dipole-Dipole Interactions.

Explanation:
                   The bond between Hydrogen and Chlorine is Polar Covalent Bond as the electronegativity difference between these two elements is 0.96 which is greater than 0.4. Chlorine being more electronegative attracts the electrons from Hydrogen making the Hydrogen partial positive and itself partial negative. The two poles on HCl makes it a dipole. Now, one HCl (a dipole) interacts with another HCl (another Dipole) through their opposite charges and creates Dipole-Dipole Interaction. The picture is as below, the green dashed lines are interactions,

If a hydrogen atom is neutral, it must also have  one electron. an oxygen atom (o) has an atomic number of eight (8). this means a neutral oxygen atom has eight protons and eight electrons. the element actium (ac) has an atomic number of 89, so it has 89 protons and 89 electrons in a neutral atom