Which of the following provides a money-back guarantee?

Priority Mail Express stands out because it offers a money-back guarantee for its delivery services. This guarantee means that if the package is not delivered by the promised time, the customer is eligible for a full refund of the postage. This service is designed for urgent shipments, providing priority handling to ensure swift delivery.

The other options do not come with a money-back guarantee. First-Class Mail and Standard Mail are primarily used for letters and parcels, with delivery times that can vary but do not include refunds for late deliveries. Priority Mail, while it provides fast shipping and includes tracking, does not include the same money-back guarantee for late deliveries, making Priority Mail Express the only option among the choices that assures a refund for failure to meet the delivery expectations.