Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R.
Assertion A: Thinning of ozone layer is more prominant over Antartica as compared to Arctic.
Reason R: Stratospheric temperature over arctic does not fall as low and for as long as it happens over Antartica and Polar stratospheric clouds form less frequently over Arctic then over Antartica.
In the light of the above statements, choose the most appropriate answer from the options given below :