As we move down a group in the periodic table, the metallic character of elements increases, which in turn increases the basic character of their oxides. Among the given options:

1. $\text{Al}_2\text{O}_3$ (Aluminium oxide) and $\text{Sb}_2\text{O}_3$ (Antimony trioxide) are amphoteric oxides.
2. $\text{SeO}_2$ (Selenium dioxide) is an oxide of a non-metal, hence it is acidic.
3. $\text{Bi}_2\text{O}_3$ (Bismuth(III) oxide) is an oxide of bismuth, a typical metal located at the bottom of Group 15. Therefore, it is the most basic oxide among the given choices.