Analysis: Simple molecules must not contain polar bonds, which is correct, because only nonpolar bonds can be formed between the same atoms.

O3 is a polar molecule. Because O3 is an angular molecule with two σ bonds and one pai43 bond, the resultant force of the bonds is not 0, so it is a polar molecule.

Note: Pai-43 bond means that one of the three O atoms provides two single electrons, and each of the two O atoms provides 1 single electron to form Pai-43 bond. This is the content of university study.