What defines shipping services offered by the Postal Service?

The correct choice highlights that the shipping services offered by the Postal Service are characterized by products where it is competitive with other delivery companies. This means that the Postal Service focuses on providing a range of shipping options that meet market demands, allowing them to compete effectively in the broader delivery and logistics sector. These services encompass various shipping classes, such as Priority Mail and First-Class Package Service, enabling customers to select options based on their needs for speed, delivery time, and pricing.

The emphasis on competition is crucial because it enables the Postal Service to adapt its offerings based on market trends, ensuring that customers receive services that are not only reliable but also cost-effective when compared to private carriers. This competitive approach allows the Postal Service to remain viable in an evolving marketplace.

While other options mention exclusive services or limitations, they do not encompass the essential characteristic of the Postal Service's offerings, which is their competitive nature in comparison to other delivery options on the market. Therefore, the focus on competitive products forms the basis of the Postal Service's shipping services.