Final answer:
Pinning is not a method of distributing a new root digital certificate; it is a security measure against fraudulent certificates. New root certificates are commonly distributed via OS, application, or web browser updates.
Step-by-step explanation:
The student is asking about the distribution methods for a newly approved root digital certificate. Out of the options provided, pinning is NOT a method by which a root digital certificate is typically distributed.
Certificate pinning is a security measure that involves hard-coding the certificate known to be valid for a particular server inside an application. This approach is used to prevent attackers from tricking the application into accepting a fraudulent certificate.
New root certificates are usually distributed through OS updates, application updates, or web browser updates. These updates ensure that the trust store containing the trusted root certificates is kept up-to-date, which allows the system to verify the authenticity of secure connections.
Therefore, the correct answer is 4) Pinning.