Which balanced equation represents a single replacement reaction?

(1) Mg + 2AgNO3 → Mg (NO3) 2 + 2Ag

(2) 2Mg + O2 → 2MgO

(3) MgCO3 → MgO + CO2

(4) MgCl2 + 2AgNO3 → 2AgCl + Mg (NO3) 2

The questions say,'which balanced equation represents a single balanced replacement reaction? The correct option is reaction 1, which is the reaction of magnesium with silver nitrate to give magnesium nitrate and silver. A single replacement reaction is a chemical reaction in which an element react with a compound and take the place of another element in that compound.