Answer: Amazon Cognito

## Explanation Amazon Cognito is the correct AWS service for this requirement because: 1. **User Authentication**: Amazon Cognito provides user authentication and authorization capabilities for mobile and web applications. 2. **Social Media Integration**: It supports federated identity through social media identity providers (IdPs) such as Facebook, Google, Amazon, and Apple, allowing users to sign in using their existing social media accounts. 3. **User Pools**: Amazon Cognito User Pools are user directories that provide sign-up and sign-in options for your app users, including social media federation. 4. **Identity Pools**: Amazon Cognito Identity Pools enable you to create unique identities for your users and federate them with identity providers, including social media providers. **Why the other options are incorrect:** - **AWS Lambda**: A serverless compute service for running code without provisioning servers, not for authentication. - **AWS Secrets Manager**: A service for storing and managing secrets like database credentials, API keys, and other sensitive information, not for user authentication. - **Amazon CloudFront**: A content delivery network (CDN) service for delivering content globally with low latency, not for authentication. Amazon Cognito is specifically designed to handle user authentication, including social media sign-in, making it the ideal choice for this mobile app requirement.

Author: Ritesh Yadav