Color of magnesium oxide is:

The correct option is A

White

• An explanation for the correct option (A)

1. Magnesium ribbon is burnt in the presence of air to form a white color powder i.e. Magnesium oxide $\left(\mathrm{MgO}\right)$.
2. Magnesium oxide is made up of ${\mathrm{Mg}}^{2+}$ and ${\mathrm{O}}^{2-}$ ions and is connected to each other by an ionic bond.

Chemical Reaction:

$\underset{\mathrm{Magnesium}}{2\mathrm{Mg}\left(\mathrm{s}\right)}+\underset{\mathrm{Oxygen}\mathrm{gas}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}\to \underset{\mathrm{Magnesium}\mathrm{Oxide}}{2\mathrm{MgO}\left(\mathrm{s}\right)}$

Hence, the correct option is (a) as the color of Magnesium oxide is white.