In order to optimize performance for a compute cluster that requires low inter-node latency, which of the
following feature should you use?

A.
Multiple Availability Zones

B.
AWS Direct Connect

C.
EC2 Dedicated Instances

D.
Placement Groups

E.
VPC private subnets

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. http://
docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html

http://aws.amazon.com/ec2/faqs/ (enhanced networking)