SSH communications are encrypted, but sometimes it is useful to try the telnet command as shown below: telnet $192\mathrm{.}168\mathrm{.}100\mathrm{.}522$

What is the use of it$?$

a$.$ Brute$-$forcing the SSH credentials

b$.$ Connecting to the Telnet service through SSH

c$.$ Creating a SSH tunnel

d$.$ Grabbing banner information