Your company has an EC2 Instance running a web application. They want to add high availability to the running instance. Which of the following is the easiest way to achieve this, ensuring no downtime for the current instance?

Answer options:

A.Create an AMI from the running instance. Create a new launch configuration and an Auto Scaling group. Terminate the current instance and launch the Auto Scaling group to launch a new instance.
B.Create an Auto Scaling group from the running EC2 Instance.
C.Terminate the instance and launch it via an Elastic Beanstalk environment.
D.Terminate the instance and launch it via an Opswork stack.

Correct Answer: B
You can create an Auto Scaling group using an existing EC2 instance in one of three ways.
Create a launch template from an existing EC2 instance. Then use the launch template to create a new Auto Scaling group. For this procedure, see Creating a launch template from an existing instance (console).
Use the console to create an Auto Scaling group from a running EC2 instance. When you do this, Amazon EC2 Auto Scaling creates a launch configuration for you and associates it with the Auto Scaling group. This method works well if you want to add the instance to the new Auto Scaling group where it can be managed by Amazon EC2 Auto Scaling. For more information, see Attach EC2 instances to your Auto Scaling group.
Specify the ID of an existing EC2 instance in the API call that creates the Auto Scaling group. This method is the subject of the following procedure.
Option A is incorrect because it leads to downtime by creating launch configuration, AMI, and Auto Scaling group.
Options C and D are incorrect because Elastic Beanstalk and Opswork stack are not easy methods and are very time-consuming. 
For more information on creating a launch configuration from an existing instance, please visit the below URL-
https://docs.aws.amazon.com/autoscaling/ec2/userguide/create-asg-from-instance.html
https://docs.aws.amazon.com/autoscaling/ec2/userguide/create-launch-template.html#create-launch-template-for-auto-scaling
https://docs.aws.amazon.com/autoscaling/ec2/userguide/create-lc-with-instanceID.html#create-lc-with-defaultconfig