Answer: (A) Firewall; implement an ACL on the interface
Step-by-step explanation:
According to the question, for re-mediate the issue firewall should be implemented the ACL (Access control list) on the given interface. The access control list is one of the type of logic which selectively give permission or deny the number of packet in the system which to through the interface.
Firewall is the type of device that basically examine the traffic in the network system and also make several decisions in the system. ACL is the set of rule which mainly define the route of the packet in the router interface state.