What is the scope of an EC2 security group?

to communicate with an instance outside its region using security group rules. Traffic from an instance in another region is seen as WAN bandwidth. http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/resources.html

A.
Availability Zone

B.
Placement Group

C.
Region

D.
VPC

Explanation:
Explanation/Reference:
A security group is tied to a region and can be assigned only to instances in the same region. You can’t enable an instance