Which of the following includes all the true statements listed below:

I. A segment includes the message constructed at the application layer and the header attached at the transport layer $($transport layer header$).$

II$.$ A frame includes the message constructed at the application layer, the transport layer header, the network layer header, and the link layer header.

III. A datagram includes the message constructed at the application layer, the network layer header, the transport layer header, and the link layer header.

IV$.$ A message constructed at the application layer includes the link layer header.

V$.$ Encapsulation is attaching the necessary header at each layer to the message constructed at the application layer.