In Salesforce, triggers can be defined to execute before or after a DML operation. An "after" trigger is used when you want to use the records that have been changed and rely on their committed values. In this scenario, you would use an after update trigger because you need to create a new record (Engineering Review) after the case has been updated with a status of "Could not fix". This cannot be done in a "before" trigger because the changes have not yet been committed to the database.
Therefore, the correct answer is A, which specifies an after update trigger on the Case object to create and insert the Engineering Review record.
References:
Salesforce Developer Documentation on Triggers: Apex Developer Guide - Triggers