How does the reversible reaction of hydrofluoric acid in water illustrate the behavior of weak electrolytes?

It shows that weak electrolytes completely dissociate, forming a static equilibrium.

It shows that weak electrolytes form covalent bonds with water molecules.

It shows that weak electrolytes do not dissociate at all, remaining as molecules.

It shows that weak electrolytes partially dissociate, forming a dynamic equilibrium between ions and molecules.