Which of the following reactions will produce a gas?

BaCl₂(aq) + Na₂SO₄(aq) → BaSO₄(s) + 2NaCl(aq)

NaCl(aq) + AgNO₃(aq) → AgCl(s) + NaNO₃(aq)

CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l) + CO₂(g)

HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)