A 50 year old Computer Solutions company has a very big application that needs to be deployed to the AWS cloud from its existing server. The application is media access control (MAC) address dependent as per the application licensing terms. This application will be deployed in an on-demand EC2 instance with instance type r4.2xlarge. In this scenario, how can you ensure that the MAC address of the EC2 instance will not change even if the instance is restarted or rebooted?

Answer options:

A.Assign static MAC Address to EC2 instance while setting up the server.
B.Use a VPC with an elastic network interface that has a fixed MAC Address.
C.Use a VPC with a private subnet for the EC2, by default MAC address will be fixed.
D.Use a VPC with a private subnet and configure the MAC address to be tied to that subnet.

Correct Answer - B 
Option A is incorrect because you cannot assign a static MAC Address to EC2 Server. If the server restarts, it will also change.
Option B is correct because for the server to be MAC Dependent, you must use VPC with an ENI (Elastic Network Interface).
Option C and D are incorrect because using a private subnet in VPC cannot help get MAC Address fixed. 
Refer: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-eni.html