Final answer:
The ozone layer in the earth's stratosphere is the subject of this question. It is seasonally centered over Antarctica but is currently shrinking due to the Montreal Protocol.
Step-by-step explanation:
The subject of this question is Geography. The question is asking about the ozone layer in the earth's stratosphere, specifically over Antarctica. The ozone layer is a layer of ozone (O3) near the top of the stratosphere that protects the Earth from harmful ultraviolet radiation from the sun. The ozone hole, which is a major reduction in ozone levels, is seasonally centered over Antarctica but is currently shrinking thanks to the Montreal Protocol.