Final answer:
A) Argon (Ar) is not an electrolyte, while sodium chloride (NaCl), rubidium sulfate (Rb2SO4), hydrochloric acid (HCl), and potassium hydroxide (KOH) are all electrolytes.
Step-by-step explanation:
An electrolyte is a substance that conducts electricity when dissolved in water.
Sodium chloride (NaCl), rubidium sulfate (Rb2SO4), hydrochloric acid (HCl), and potassium hydroxide (KOH) are all electrolytes because they dissociate into ions in water and allow an electric current to flow.
On the other hand, argon (Ar) is not an electrolyte because it does not dissociate into ions when dissolved in water.