Answer – A,C and D
The AWS documentation mentions the following on enabling the Elastic Network Adapter
· Launch the instance from an HVM AMI using Linux kernel version of 3.2 or later. The latest Amazon Linux HVM AMIs have the modules required for enhanced networking installed and have the required attributes set. Therefore, if you launch an Amazon EBS–backed, enhanced networking–supported instance using a current Amazon Linux HVM AMI, ENA enhanced networking is already enabled for your instance.
· Launch the instance in a VPC. (You can`t enable enhanced networking if the instance is in EC2-Classic.)
http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/enhanced-networking-ena.html