Answer:
<em><u>Metal oxides</u></em>
Explanation:
Al2O3, ZnO and SnO are typical amphoteric oxides. Metal oxides are usually basic and they react with acids to form their respective salts
Since chromium has 24 as its atomic number (which mean that it has 24 proton and 24 electron in neutral ground state), the electron configuration for the chromium would be :
1s^2 , 2s^2 , 2p^6 , 3s^2, 3p^6 , 3d^5 , 4s^1
Among all of the choices listed, the only option that is a base would be the last one. As it is unique, whereby Hydrogen is not present in the front of the compound.
Bases also possess OH in their molecular formula.