Your mobile application includes a photo-sharing service that is expecting tens of thousands of users at launch. You will leverage Amazon Simple Storage Service (S3) for storage of the user Images, and you must decide how to authenticate and authorize your users for access to these images. You also need to manage the storage of these images.
Which two of the following approaches should you use? (Choose two.)

A. Create an Amazon S3 bucket per user, and use your application to generate the S3 URI for the appropriate content.
B. Use AWS Identity and Access Management (IAM) user accounts as your application-level user database, and offload the burden of authentication from your application code.
C. Authenticate your users at the application level, and use AWS Security Token Service (STS) to grant token-based authorization to S3 objects.
D. Authenticate your users at the application level, and send an SMS token message to the user. Create an Amazon S3 bucket with the same name as the SMS message token, and move the user's objects to that bucket.
E. Use a key-based naming scheme comprised from the user IDs for all user objects in a single Amazon S3 bucket.