You currently have 2 instances (c4.large) in a VPC. You plan to create a placement group because now there is a requirement for better network communication between the instances. You are planning to move the already created instances to this placement group. But you encounter an issue. Which of the below could be a legitimate issue?

Answer options:

A.The Instance type of the instances are not supported in the placement group.
B.You can`t have Linux Instances in a placement group
C.You can`t move an existing instance into a placement group
D.You can`t have Instances with EBS volumes in a placement group

Answer - C
The AWS documentation mentions the following
You can`t move an existing instance into a placement group. You can create an AMI from your existing instance, and then launch a new instance from the AMI into a placement group.
For more information on placement groups, one can visit the below URL:
http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html
Note: This question is marked for replacement.
Now with lastest AWS update you can move existing instance to a Placement Group.
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html#change-instance-placement-group