The most likely true statement about a package that Kristina sends via certified mail is: The receiver must provide a signature at the time of delivery.
Certified mail requires that the recipient signs for the package upon delivery, providing proof of delivery. While compensation for damages may be available under certain circumstances, it is not guaranteed and is not an inherent feature of certified mail itself. A green card indicating the recipient's signature is associated with the service, but it's the signature requirement that is most definitive about the nature of certified mail. Secure handling of the package is a goal, but it cannot be guaranteed.