Which of the following protocols is used to transfer files over the Internet?

SNMP (Simple Network Management Protocol) is used to monitor and manage network devices such as routers and switches, not to transfer files.

NTP (Network Time Protocol) synchronizes clocks across networked devices and does not transfer files.

FTP (File Transfer Protocol) operates on TCP ports 20 (data) and 21 (control) and provides a dedicated mechanism for uploading and downloading files between a client and server over the Internet. It supports authentication, directory navigation, and bulk file transfers, making it the standard protocol purpose-built for file transfer.

SIP (Session Initiation Protocol) establishes, manages, and terminates multimedia communication sessions such as VoIP calls, not file transfers.