An element $X$ (atomic number $17$) reacts with an element $Y$ (atomic number $20$) to form a divalent halide. What will be the nature of oxide of element Y?

The correct option is A Basic
Y has 20 electrons, i.e., calcium. It must be in the 4th period and as it has to donate 2 electrons to get the stable configuration of [Ar]. It is calcium and it forms basic oxide.