Incomplete question, the complete question is written below
An aqueous solution of which of the following compounds is the best conductor of electric current?
A. Ammonia NH3.
B. Fructose C6H12O6.
C. Acetic acid C2H4O2.
D. Hydrochloric acid HCl.
Answer
D. Hydrochloric acid HCl
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.
Dissolution of HCl
HCl → H+ + Cl-
The positive ion Hydrogen moves to the cathode, so they are called cations
The negative ions Chlorine moves to the anode, and they are called anions.
Conductivity can be increased by increasing the concentration of charge carriers (ions) in an aqueous solution. An aqueous hydrochloric acid solution will conduct electricity very well. However each of the ions has only a single charge--hydrogen is +1 and chloride is -1.