A large financial services company requires that all data be encrypted in transit. A Developer is attempting to connect to an Amazon RDS DB instance using the company VPC for the first time with credentials provided by a Database Specialist. Other members of the Development team can connect, but this user is consistently receiving an error indicating a communications link failure. The Developer asked the Database Specialist to reset the password a number of times, but the error persists.
Which step should be taken to troubleshoot this issue?

A. Ensure that the database option group for the RDS DB instance allows ingress from the Developer machine's IP address
B. Ensure that the RDS DB instance's subnet group includes a public subnet to allow the Developer to connect
C. Ensure that the RDS DB instance has not reached its maximum connections limit
D. Ensure that the connection is using SSL and is addressing the port where the RDS DB instance is listening for encrypted connections