FTP uses TCP to establish two virtual connections - one for data and another for commands.
TFTP (Trivial File Tnansfer Protocol) uses UDP. So this option is ruled out.
In Telnet, user data is send in-band with control information over a single 8-bit byte oriented data connection. So only one virtual connection is needed.
NFS is a distributed filesystem. Originally, it was implemented to run on top of UDP, though some implementations allow TCP connections. But in that case also, by default, an NFS client uses only a single TCP connection to each NFS server, regardless of how many NFS filesystems are mounted by the client.
So, in short the correct answer is option (A) - FTP.
