The reaction given is:
NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)
This reaction is classified as a double replacement reaction. In a double replacement reaction, the anions and cations of two different compounds switch places to form two new compounds. In this case, the hydroxide (OH⁻) from NaOH and the hydrogen (H⁺) from HCl combine to form water (H2O), while Na⁺ and Cl⁻ combine to form sodium chloride (NaCl).
So the correct response is:
double replacement.