Which of the following is true while using an IAM role to grant permissions to applications running
on Amazon EC2 instances?

A.
All applications on the instance share the same role, but different permissions.

B.
All applications on the instance share multiple roles and permissions.

C.
Multiple roles are assigned to an EC2 instance at a time.

D.
Only one role can be assigned to an EC2 instance at a time.

Explanation:
Only one role can be assigned to an EC2 instance at a time, and all applications on the instance
share the same role and permissions.
http://docs.aws.amazon.com/IAM/latest/UserGuide/role-usecase-ec2app.html