Final answer:
An application that operates on port 53 and resides at the application layer of the TCP/IP protocol stack is likely a DNS server.
Step-by-step explanation:
An application that operates on port 53 and resides at the application layer of the TCP/IP protocol stack is likely a DNS server. DNS (Domain Name System) servers are responsible for translating human-readable domain names (like www.example.com) into machine-readable IP addresses (like 192.168.1.1).