A User Has Configured a VPC with a New Subnet

Multiple Choice

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