Which of the following are valid properties of Placement Groups? Choose 3 answers from the list of options given below.

Answer options:

A.A cluster placement group can span across multiple AZ`s.
B.Placement groups can`t be merged
C.An instance can be launched in one placement group at a time; it cannot span multiple placement groups
D.You can`t move an existing instance into a Placement Group.
E.If you want to delete a Placement Group you need to terminate or move all instances from it.

Answer - B,C and E
Option A is Incorrect. A cluster placement group is a logical grouping of instances within a single Availability Zone. 
Option D is Incorrect. You can move an existing instance into a Placement Group.
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html
The limitations on placement groups are
1) A placement group can`t span multiple Availability Zones
2) You can`t merge placement groups
3) A placement group can span peered VPCs
For more information on placement groups , just browse to the below URL:
http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html