Which of these is a service provided by the USPS?

International Mail is indeed a service provided by the USPS, allowing customers to send letters and packages to destinations outside of the United States. This service encompasses a variety of mailing options tailored for international delivery, including various speeds and pricing tiers, depending on the destination and type of mail.

The importance of this service lies in its ability to connect individuals and businesses across the globe, making it essential for personal correspondence, business operations, and e-commerce ventures that involve international customers. Additionally, USPS provides tracking for many international services, enhancing the customer experience by offering peace of mind about the status of their mail.

The other options listed do not pertain to services offered by USPS. UPS Next Day Air and DHL Express are both services provided by private shipping companies, while First Class Mail International is a specific service under the broader category of International Mail. In this context, understanding the breadth of USPS's services helps clarify the correct answer.