The species containing unpaired electron will show paramagnetic nature. Among the given options, all the metal ions have only paired electrons, so whether the compound is magnetic or not depends on the anion in each case. In case of silicon dioxide and titanium oxide, O^2- is present which doesn't have unpaired electrons. In case of Barium peroxide, the peroxide ion (O₂^2-) also has only paired electrons and hence the compound is diamagnetic.

In case of potassium superoxide, O₂^- ion has unpaired electron and this will give the compound paramagnetic nature.