the two hosts without further checking?

What type of firewall works on the Session layer that creates a connection and allows packets to flow between
the two hosts without further checking?

A.
proxy server

B.
application firewall

C.
NAT filtering

D.
circuit-level gateway

Explanation:
Section Reference: Defining Firewalls and Other Perimeter Security Devices
A circuit-level gateway works at the Session layerof the OSI model when a TCP or UDP connection is
established. When the connection is made, packets can flow between hosts without further checking. Circuit-level gateways hide information about the private network, but they do not filter individual packets.