Answer:
That the hydrochloric acid reacted with the sodium sulfide to produce the same gas that is formed from rotten eggs.
Explanation:
The equation for the reaction for the reaction is
Na₂S(aq) + 2HCl(aq) ⟶ 2NaCl(aq) + H₂S(g)
sodium sulfide + hydrochloric acid ⟶ sodium chloride + hydrogen sulfide