Is PbO ionic compound? In IIT-JAM 2018, There was one question, which one of the following oxides are ionic?
There was one option PbO also. According to the official answer key, PbO isn't ionic.

Although I know this distinction between ionic and covalent isn't defined sharply. But Pb 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 PbO, although PbO2 is defined in between of ionic and covalent according to this paper. PbO should be more ionic than PbO2 since oxidation state of the Pb is lower, it will be less electronegative.

Even $\ce{PbCl2}$  is considered as Ionic according to many books, where Cl is less electronegative and much bigger in size as compared to O, So At least 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?


Iono-Covalent Character of the Metal–Oxygen Bonds in Oxides: A Comparison of Experimental and Theoretical Data
If you want a reference to challenge the question, try page 248 of Advanced Study Guide Chemistry.  There is a table on that page that says the PbO is "ionic".