Which is the world's most southernmost wine region?

Central Otago is the correct response because it is recognized as the southernmost wine region in the world, located in New Zealand's South Island. This region is known for its unique climate, which is influenced by its latitude, elevation, and geographical features. Central Otago's cool temperatures and significant sunlight hours create ideal conditions for growing high-quality Pinot Noir, among other varieties. The deep, mountainous landscapes and the climate contribute to the development of distinctive wine profiles that have garnered international acclaim.

In comparison to the other options, while Ushuaia in Argentina is famous for being the southernmost city and a potential wine-producing area, it isn't classified specifically as a wine region in the same context as Central Otago. Cape Horn is primarily known for its extreme geographic position at the southern tip of South America and does not have a significant wine industry. Auckland, although it is a notable wine-producing area in New Zealand, is located much further north than Central Otago. Thus, the combination of geographical positioning and the extent of viticulture development solidifies Central Otago's place as the most southernmost wine region globally.