A Developer Is Writing a Mobile Application That Allows Users

A Developer is writing a mobile application that allows users to view images from an S3 bucket. The users must be able to log in with their Amazon login, as well as Facebook® and/or Google® accounts. How can the Developer provide this authentication functionality?

A) Use Amazon Cognito with web identity federation.
B) Use Amazon Cognito with SAML-based identity federation.
C) Use AWS IAM Access/Secret keys in the application code to allow Get* on the S3 bucket. Use AWS IAM Access/Secret keys in the application code to allow Get* on the S3 bucket.
D) Use AWS STS AssumeRole in the application code and assume a role with Get* permissions on the S3 bucket. Use AWS STS AssumeRole in the application code and assume a role with permissions on the S3 bucket.