How do you enable a default connection between Database…

How do you enable a default connection between Database as a Service (DBaaS) instances?

A.
by creating network groups and adding the instances that you want to communicate to that group

B.
by creating dedicated communication keys and setting them to be used only for your DBaaS instance-to-instance communication

C.
by creating nothing for communication between the DBaaS instances because all instances are interconnected by default

D.
by installing and configuring the NETMGR utility for your DBaaS environment, and then using it to set up the required communication channels

Explanation:
Before your DBaaS database was created, you or a coworker generated a private and public SSH key pair, perhaps using PuTTY Key Generator.
The public key was specified when your database instance was created; a copy of that public key was stored in the VM hosting your database.
When you define in PuTTY an SSH connection to the VM hosting your database, you will specify a copy of the private key stored on your local PC. When you initiate
a PuTTY connection, the VM compares the private key to the matching public key stored in the VM. The VM permits the connection when the private and public key
match as a valid key pair.
http://www.oracle.com/webfolder/technetwork/tutorials/obe/cloud/dbaas/obe_dbaas_connecting_to_an_instance/

obe_dbaas_connecting_to_an_instance.html