Right answer is (c) Network layer or Transport layer
Explanation: In computing, a firewall is a network security system that monitors and controls the incoming and outgoing network traffic based on predetermined security rules.[1] A firewall typically establishes a barrier between a trusted, secure internal network and another outside network, such as the Internet, that is assumed not to be secure or trusted.[2] Firewalls are often categorized as either network firewalls or host-based firewalls.
