Assertion A is correct: although CFCs (chlorofluorocarbons) released at the earth's surface get mixed fairly evenly throughout the global atmosphere, the depletion of the ozone layer is far more severe over Antarctica (the south pole) than elsewhere, giving rise to the well-known seasonal "ozone hole."
Reason R is not correct as worded: the presence of ice crystals over the south pole does not make chlorine-to-oxygen bonding "tougher." The real scientific explanation is quite different — during the extremely cold, dark Antarctic winter, a strong, isolated polar vortex traps air over the continent, and the intense cold allows polar stratospheric clouds (made of ice crystals) to form. The surfaces of these ice-crystal clouds actually provide sites for heterogeneous chemical reactions that convert otherwise stable, unreactive chlorine "reservoir" compounds (like HCl and ClONO2) into forms that can be readily broken down by sunlight. When sunlight returns in spring, this reactive chlorine is released and rapidly, catalytically destroys ozone molecules, producing the seasonal ozone hole.
So the ice crystals actually help liberate reactive chlorine (which then destroys ozone) rather than strengthening any chlorine-oxygen bond — the mechanism proposed in Reason R misrepresents the underlying chemistry, even though the outcome described in Assertion A is scientifically accurate.
Hence, Assertion A is correct but Reason R is not correct.