Aqueous solution of which of the following compounds is the best conductor of electric current?

The aqueous solution of Hydrochloric acid, HCl is the best conductor of electric current as it is a strong electrolyte and is completely dissociated into ions. On the other hand, ammonia and acetic acid are weak electrolytes which undergo partial dissociation and fructose is a non-electrolyte. Hence, they are poor conductors of electricity. Hence, the correct option is Hydrochloric acid, HCl.