What is the strongest intermolecular force between a NaCl unit and an H2O molecule together in a solution?

A. Covalent bonding

B. Dipole-dipole force

C. Hydrogen bonding

D. Ion-dipole force

D Seems most correct

Ion dipole force.

Explanation:

When sodium chloride is dissolved in water it dissociates into sodium ion and chloride ion.

Sodium ion has positive charge on it.

Chloride ion has negative charge on it.

In water molecule, due to electronegativity difference, hydrogen acquires a slightly positive charge and oxygen a slightly negative charge.

This creates a dipole in water molecule.

Now the force of attraction between water and NaCl is in between the ions and the dipole.

Thus the strongest intermolecular force of attraction between NaCl and water is Ion-dipole.