Which protocol is used for secure communication over a computer network?

The correct choice is HTTPS because it is specifically designed to provide a secure version of HTTP (HyperText Transfer Protocol). HTTPS incorporates encryption protocols such as SSL (Secure Sockets Layer) or TLS (Transport Layer Security) to encrypt data transmitted over the network, ensuring that the information exchanged between the client and server remains confidential and protected from interception by unauthorized parties. This is particularly important for safeguarding sensitive information such as passwords, personal data, and financial transactions during online communications.

In contrast, the other protocols mentioned do not inherently provide security features. HTTP, for example, transmits data in plaintext, making it vulnerable to eavesdropping. FTP (File Transfer Protocol) primarily handles file transfers but lacks built-in encryption, leaving data exposed. SMTP (Simple Mail Transfer Protocol) is used for sending emails but does not focus on secure transmission of email content by default. Therefore, HTTPS is the preferred protocol for secure communications over a computer network, making it the correct answer.