Question

what data unit is encapsulated inside a packet?
segment
frame
datagram
session

Explanation:

In networking, a packet is a unit of data at the network - layer. A segment from the transport - layer is encapsulated inside a packet at the network - layer. Frames are at the data - link layer and encapsulate packets. Datagrams are also related to the network layer but are a different concept from what is directly encapsulated in a packet. A session is related to the session - layer and not a data unit encapsulated in a packet.

Answer:

A. segment