Application-layer protocols provide network services directly to user applications and define how clients and servers exchange application data. DNS is an application-layer protocol used to translate domain names into IP addresses (and perform related record lookups), enabling applications to locate services by name instead of by numeric address. Telnet is also an application-layer protocol that provides remote terminal access; it allows a user to interact with a remote system's command-line interface over the network (though it is insecure because it transmits data in plaintext). HTTP is an application-layer protocol used for web communication, defining request/response behavior between browsers (clients) and web servers for transferring web pages and related content.
In contrast, ARP is not an application-layer protocol. ARP operates at the boundary of Layer 2/Layer 3 to map an IPv4 address to a MAC address on the local network segment, supporting frame delivery on Ethernet.
Therefore, the application-layer protocols here are DNS, Telnet, and HTTP.