Choose which of the following correctly complete these reactions:

Metal oxide + Acid $\to$ Metal salt
I)${\mathrm{Na}}_2\mathrm{O}+2\mathrm{HCl}\to$
II) $\mathrm{MgO}+{\mathrm{H}}_2{\mathrm{SO}}_4\to$
III) ${\mathrm{K}}_2\mathrm{O}+{\mathrm{HNO}}_3\to$

Metal oxides are understood to be oxides of metal that include the cation of the metal and the anion of the oxide. A metal can generate oxides, peroxides, and superoxides, which are three different forms of oxides. Compounds containing an oxygen atom attached to another atom are called oxides.
Metal salts and water are produced when metal oxides and acids interact.
Let's talk about the available choices:
Sodium chloride and water are produced when hydrogen chloride and sodium oxide are combined.
Let's observe the response.

${\mathrm{Na}}_2\mathrm{O}+2\mathrm{HCl}\to 2\mathrm{NaCl}+{\mathrm{H}}_2\mathrm{O}$

When sulfuric acid and magnesium oxide are combined, magnesium sulfate and water are produced. In this case, magnesium oxide is a basic oxide that balances acids and produces the metal salt magnesium sulphate.
Let's observe the response.

$\mathrm{MgO}+{\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{MgSO}}_4+{\mathrm{H}}_2\mathrm{O}$

Potassium nitrate and water are produced as a result of the reaction between potassium oxide and nitric acid. Here, potassium oxide, a basic oxide, balances the acid by forming potassium nitrate, a metal salt.
Let's observe the response.

${\mathrm{K}}_2\mathrm{O}+2{\mathrm{HNO}}_3\to 2{\mathrm{KNO}}_3+{\mathrm{H}}_2\mathrm{O}$

Hence, the correct option is A.