Which of the following is a protocol supported by SNS?

The correct answer is SMS, which stands for Short Message Service. Amazon Simple Notification Service (SNS) supports SMS as one of its protocols, allowing users to send messages directly to mobile devices via text messaging. This capability is particularly useful for sending notifications, alerts, or marketing messages directly to end-users' phones, enhancing communication and engagement through a platform that many people routinely check.

In the context of SNS, SMS is one of several communication protocols available, alongside others such as email, application notifications, and HTTP/S endpoints. The ability to send messages via SMS adds significant versatility and reliability to notification strategies, especially for time-sensitive information.

The other options listed—Amazon S3, Amazon CloudFront, and Amazon RDS—are not protocols supported by SNS. Instead, they represent different AWS services used for storage, content delivery, and database management, respectively. Each of these services functions independently and does not align with the messaging capabilities of SNS, highlighting the focused purpose of SNS in facilitating communication through various channels, including SMS.