A company uses a hybrid solution that syncs data between on$-$premises and cloud DBMS virtual servers. Database administrators $($DBAs$)$ can set up the cloud network within the cloud web portal to ensure security and privacy. What must DBAs also configure on$-$premises to ensure a secure connection to the cloud's network?

a$.$

Install a signed certificate to the DBMS application.

b$.$

Setup complex password requirements for DBAs.

c$.$

Encrypt the database storage.

d$.$

Configure a virtual private network.