The correct answer is A. An Azure region contains one or more data centers that are connected by using a low-latency network. This design ensures that Azure services within any region offer the best possible performance and security. The other options are incorrect because Azure regions are not necessarily found in each country where Microsoft has a subsidiary office (B), they are not limited to Europe and the Americas (C), and they use low-latency network connections rather than high-latency ones (D).