How does SNS send notifications to its subscribers?

Amazon Simple Notification Service (SNS) is designed to facilitate effective message delivery to subscribers through a variety of communication protocols. The correct option highlights that SNS sends notifications by using HTTP/S requests or push notifications.

When a user publishes a message to an SNS topic, all subscribers to that topic receive the message via the communication protocol they've chosen. This can include push notifications to mobile devices through services like Apple Push Notification Service (APNs) or Google Cloud Messaging (GCM), as well as delivering messages to HTTP/S endpoints where a web server can process them.

The versatility of SNS in sending notifications is one of its key features, allowing applications to communicate seamlessly regardless of the type of subscriber—whether it be an email address, an SMS-capable device, or an HTTP endpoint. This makes it an ideal choice for applications that require robust and scalable notification systems. In contrast to the other mentioned methods, such as batch processing or direct database connections, which are not utilized by SNS for sending notifications, the use of HTTP/S requests or push notifications is directly in line with the service's designed functionality.