Which of the following sets correctly describes the nature of $\mathrm{CrO}$, $\mathrm{Cr}{}_2\mathrm{O}{}_3$ and $\mathrm{CrO}{}_3$ in that order?

For a given metal the electronegativity and the polarising power of the metal rise with the oxidation state, so the oxide changes from basic to acidic. $\mathrm{CrO}$ (+2) is basic, $\mathrm{Cr}{}_2\mathrm{O}{}_3$ (+3) is amphoteric and $\mathrm{CrO}{}_3$ (+6) is acidic, giving chromic acid with water.