How are errors in an SAP S/4HANA migration handled?

You start your first sandbox migration and get a lot of errors.

How are errors in an SAP S/4HANA migration handled? There are 2 correct answer to this question.
A . All errors must be corrected during migration to complete it.
B . All errors related to closed years can be ignored.
C . Errors must be clarified, and uncritical errors can be ignored
D . Critical errors must be resolved in the production system before Go Live.

Answer: A,D