Which protocol is used for secure data transmission over the internet?

HTTPS, which stands for Hypertext Transfer Protocol Secure, is the correct answer as it is specifically designed for secure data transmission over the internet. It operates by encrypting data exchanged between a user's browser and the web server. This encryption protects sensitive information, such as personal details and credit card numbers, from being intercepted by malicious actors during transmission.

HTTPS uses protocols like SSL/TLS to establish a secure connection, which ensures that any data sent between the client and server remains confidential and integral. This is particularly essential for online transactions and any situation where data security is crucial.

The other protocols mentioned do not provide the same level of security. FTP is primarily used for transferring files without encryption, making it vulnerable to interception. HTTP, while a widely used protocol for transferring web pages, does not encrypt the data transmitted, exposing it to potential security threats. SMTP, which is used for sending emails, also does not enforce encryption by default, although it can be secured with additional protocols.