The oxide which can react with $\mathrm{HCl}$ as well as $\mathrm{KOH}$ to give corresponding salt and water is

According to the NCERT text, metal oxides are generally basic in nature. However, some metal oxides, such as aluminium oxide ($\mathrm{Al}_2\mathrm{O}_3$) and zinc oxide ($\mathrm{ZnO}$), show both acidic as well as basic behaviour. Such oxides are called amphoteric oxides. They react with both acids (like $\mathrm{HCl}$) and bases (like $\mathrm{KOH}$) to produce salt and water.

Reaction with acid:

$$\mathrm{Al}_2\mathrm{O}_3 + 6\mathrm{HCl} \rightarrow 2\mathrm{AlCl}_3 + 3\mathrm{H}_2\mathrm{O}$$

Reaction with base:

$$\mathrm{Al}_2\mathrm{O}_3 + 2\mathrm{KOH} \rightarrow 2\mathrm{KAlO}_2 + \mathrm{H}_2\mathrm{O}$$

• Option A ($\mathrm{CuO}$) is incorrect because copper(II) oxide is a basic oxide and does not react with bases like $\mathrm{KOH}$.
• Option C ($\mathrm{Na}_2\mathrm{O}$) and Option D ($\mathrm{K}_2\mathrm{O}$) are incorrect because they are highly basic oxides that dissolve in water to form strong alkalis ($\mathrm{NaOH}$ and $\mathrm{KOH}$ respectively) and do not react with bases.