Which example task should a developer use a trigger rather than a workflow rule for?
A. To set the primary contact on an account record when it is saved
B. To notify an external system that a record has been modified
C. To set the name field of an expense report record to expense and the date when it is saved
D. To send an email to a hiring manager when a candidate accepts a job offer

A. To set the primary contact on an account record when it is saved

Explanation:

After updating a Contact and then you set the Primary checkbox, the contact becomes the primary contact and this then updates the reference in the Parent Account. Triggers are used for this purpose and not workflow rule. In this case there is only one contact at a time that is set as Primary Contacts, and in the case where an Account does not have any Contacts, the first contact that is created is made the primary and the trigger sets that value in reference.

ok that sounds like a app that my brother would like