You are deploying an application on Amazon EC2 that must call AWS APIs. Which method would you use to allow the application access to the APIs securely?

Answer options:

A.Pass API credentials to the instance using Instance userdata.
B.Store API credentials as an object in Amazon S3.
C.Embed the API credentials into your application.
D.Assign IAM roles to the EC2 Instances.

Correct Answer - D
AWS Documentation mentions the following:
You can use roles to delegate access to users, applications, or services that don`t normally have access to your AWS resources. It is not a good practice to use IAM credentials for a production-based application. However, it is a good practice to use IAM Roles.
For more information on IAM Roles, please visit the following URL:
https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles.html