Which of the following reactions is a double replacement reaction?

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A double replacement reaction is also known as a precipitation reaction, where two ionic compounds exchange ions to form two new compounds. In this reaction, HCl and NaOH exchange ions to form NaCl and H2O. This is a precipitation reaction because NaCl is a solid (precipitate) that forms from the reaction of the two aqueous solutions. B is a single replacement reaction because magnesium (Mg) replaces hydrogen (H) in the HCl, resulting in the formation of hydrogen gas (H2) and magnesium chloride (MgCl2). C is a hydrate formation reaction because water (H2O) is added to calcium chloride (CaCl2) to form a hydrated compound with two water molecules attached (CaCl2∙2H2O). D is a decomposition reaction because potassium chlorate (KClO3) breaks down into potassium chloride (KCl) and oxygen gas (O2) when heated.

Which of the Following Reactions Is a Double Replacement Reaction