Which of the following is recommended to use when accessing AWS resources from EC2 Instances

Answer options:

A.Use the root access keys
B.Define an IAM user and use the access keys attached to the user
C.Consider implementing IAM Roles
D.Segregate IAM users into groups

Answer - C
IAM roles and temporary security credentials address these use cases. An IAM role lets you define a set of permissions to access the resources that a user or service needs, but the permissions are not attached to a specific IAM user or group. Instead, IAM users, mobile and EC2-based applications, or AWS services (like Amazon EC2) can programmatically assume a role
For more information on IAM Roles please visit the below URL:
http://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles.html