What is a placement group?

A.
A collection of Auto Scaling groups in the same Region

B.
Feature that enables EC2 instances to interact with each other via nigh bandwidth, low latency connections

C.
A collection of Elastic Load Balancers in the same Region or Availability Zone

D.
A collection of authorized Cloud Front edge locations for a distribution

Explanation:
A placement group is a logical grouping of instances within a single Availability Zone. Using placement groups enables
applications to participate in a low-latency, 10 Gigabits per second (Gbps) network. Placement groups are recommended
for applications that benefit from low network latency, high network throughput, or both. To provide the lowest latency,
and the highest packet-per-second network performance for your placement group, choose an instance type that supports
enhanced networking
http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html