How can the user configure this with the security group?

A user has configured a VPC with a new subnet. The user has created a security group. The user
wants to configure that instances of the same subnet communicate with each other. How can the
user configure this with the security group?

A.
There is no need for a security group modification as all the instances can communicate with
each
other inside the same subnet

B.
Configure the subnet as the source in the security group and allow traffic on all the protocols
and
ports

C.
Configure the security group itself as the source and allow traffic on all the protocols and ports

D.
The user has to use VPC peering to configure this

Explanation:
A Virtual Private Cloud (VPC. is a virtual network dedicated to the user’s AWS account. AWS
provides two features that the user can use to increase security in VPC: security groups and
network ACLs. Security groups work at the instance level. If the user is using the default security
group it will have a rule which allows the instances to communicate with other. For a new security
group the user has to specify the rule, add it to define the source as the security group itself, and
select all the protocols and ports for that source.