Which protocol encrypts HTTP traffic to ensure secure transactions online?

The choice of Hypertext Transfer Protocol Secure (HTTPS) is correct because it specifically refers to the secure version of HTTP, which integrates Transport Layer Security (TLS) or its predecessor, Secure Sockets Layer (SSL). HTTPS encrypts the data exchanged between a user's web browser and the web server, ensuring that any sensitive information, such as passwords or credit card details, is protected while in transit. This is crucial for maintaining user privacy and security during online transactions.

In this context, while Transport Layer Security is essential to the encryption process, it functions within the framework of HTTPS to secure HTTP traffic. Therefore, identifying HTTPS as the correct answer emphasizes the complete protocol that is recognized for securing web communications. Other protocols listed do not relate to securing web traffic directly, illustrating why they are not appropriate responses to the question about encrypting HTTP traffic.