Which of the following types of firewalls ensures that the packets are part of the established session?

A.
Stateful inspection firewall

B.
Circuit-level firewall

C.
Application-level firewall

D.
Switch-level firewall

Explanation:
A stateful firewall is a network firewall that tracks the operating state and characteristics of network connections
traversing it. The firewall is configured to distinguish legitimate packets for different types of connections. Only
packets matching a known active connection (session) are allowed to pass the firewall.
https://en.wikipedia.org/wiki/Stateful_firewall