A User Has Created a Mobile Application Which Makes Calls

Multiple Choice

A user has created a mobile application which makes calls to DynamoDB to fetch certain data. The application is using the DynamoDB SDK and root account access/secret access key to connect to DynamoDB from mobile. Which of the below mentioned statements is true with respect to the best practice for security in this scenario?

A) The user should create a separate IAM user for each mobile application and provide DynamoDB access with it
B) The user should create an IAM role with DynamoDB and EC2 access. Attach the role with EC2 and route all calls from the mobile through EC2
C) The application should use an IAM role with web identity federation which validates calls to DynamoDB with identity providers, such as Google, Amazon, and Facebook
D) Create an IAM Role with DynamoDB access and attach it with the mobile application