I’m not understanding this , any ?

Answer;

B. 2HCl + Mg(OH)2 → 2H2O + MgCl2

Explanation;The reaction of an acid with a base is called a neutralization reaction. Neutralization reaction involves reaction of a base and an acid to form salt and water as the only products. For example; the reaction of hydrochloric acid, HCl with magnesium hydroxide, Mg(OH)2 producing, sodium chloride which is a salt, and water.