Final answer:
The best action for organization super-admins to take upon receiving notifications of upcoming or sudden departures is to quickly remove the users from the Hootsuite Organization.
Step-by-step explanation:
A security-related best practice is to have a notification procedure in place that alerts organization super-admins about any upcoming and/or sudden departures so they can take appropriate action. In this case, option A) is the most suitable choice: quickly removing these users from the Hootsuite Organization. By revoking their access to the organization's Hootsuite account, the super-admins can ensure that departing employees no longer have the ability to post or make changes to the organization's social media accounts.