Explanation/Reference:
Explanation:
C: SSH is a cryptographic network protocol that uses two keys, one public and one private, to provide secure communication between two networked computers. Port 22 is the standard TCP/IP port that is assigned to SSH servers.
B: To access network protocols and services on a compute node by using a port other than port 22, you must either:
Enable network access to the port

You can use the Oracle Database Cloud Service console to enable access to a port on a compute node.
Create an SSH tunnel to the port

Creating an SSH tunnel enables you to access a specific compute node port by using an SSH connection as the transport mechanism. To create the tunnel, you must have the SSH private key file that matches the public key specified during the database deployment creation process.
References: Using Oracle Database Cloud Service (February 2017), 3-2
https://docs.oracle.com/en/cloud/paas/database-dbaas-cloud/csdbi/using-oracle-database-cloud- service.pdf