Which two statement are correct about certified delivery confirmation?

When confirmation reaches the certified listener, the transport presents DELIVERY.CONFIRM advisory.

Automatic confirmation of message delivery upon return from the callback function is the default behavior.

Explicit confirmation of message delivery by the listening program is the default behavior.

When confirmation reaches the certified sender, the transport presents DELIVERY.CONFIRM advisory.

When confirmation reaches the certified sender, the transport presents a DELIVERY.CONFIRM advisory.