Which protocol is commonly used in conjunction with SSL to secure network communications?

HTTPS is the correct answer because it is essentially an extension of the HyperText Transfer Protocol (HTTP) that incorporates SSL/TLS protocols to provide secure communication over a computer network. When data is transmitted using HTTPS, the information is encrypted, ensuring that it remains confidential and protected from interception during transmission.

This security mechanism is crucial for sensitive transactions, particularly when users are inputting personal or financial information on websites. HTTPS helps authenticate the website's identity and secures the exchange of data, making it a fundamental protocol for secure browsing and online commerce.

The other options, while related to network communication, do not serve the same purpose in conjunction with SSL as HTTPS does. FTP, for example, is used for transferring files but does not inherently offer security unless modified (like using FTPS or SFTP). SSH provides a secure channel over an unsecured network but is not directly tied to securing web communications like HTTPS. Telnet is a protocol for text-based communication and lacks encryption, making it unsuitable for any secure communication when compared to HTTPS.