In IIT-JAM 2018, There was one question: "which one of the following oxides are ionic?" I have selected $\ce{PbO}$ but according to the official answer key, $\ce{PbO}$ isn't ionic.
Although I know this distinction between ionic and covalent isn't defined sharply. But lead is a metal and oxygen is a non-metal. So according to me, it should be ionic. I tried to find on the internet I couldn't able to find out about $\ce{PbO}$, although $\ce{PbO2}$ is defined in between of ionic and covalent according to this paper. $\ce{PbO}$ should be more ionic than $\ce{PbO2}$ since oxidation state of the lead is lower, it will be less electronegative.
Even $\ce{PbCl2}$ is considered as Ionic according to many books, where chlorine is less electronegative and much bigger in size as compared to oxygen, So at least $\ce{PbO}$ should have more ionic character than $\ce{PbCl2}$ according to the Fazan's rule.
So should I challenge the official answer key? If yes, then on what basis? Which reference should I send to them?