Which protocol is commonly used for secure online transactions?

• A. HTTP
• B. FTP
• C. HTTPS
• D. SMTP

Answer: (C)

The protocol commonly used for secure online transactions is HTTPS. This stands for Hypertext Transfer Protocol Secure. HTTPS is an extension of HTTP and utilizes encryption protocols such as SSL (Secure Sockets Layer) or TLS (Transport Layer Security) to provide a secure communication channel over the internet.

When you see 'HTTPS' in a web address, it indicates that any data transmitted between the user's web browser and the server is encrypted, which makes it much harder for third parties to intercept or alter the information being exchanged. This is particularly crucial for online transactions, where sensitive information such as credit card numbers and personal details are shared.

Other protocols like HTTP, FTP, and SMTP serve different purposes and do not provide the same level of security. HTTP, for example, is used for standard web browsing but does not include encryption. FTP is used for transferring files but lacks built-in security and does not encrypt data in transit. SMTP is used for sending emails and also does not inherently provide secure transmission without additional protocols. Thus, HTTPS is essential for ensuring secure online transactions, making it the correct choice.