What could be the cause of the error?

Universal Containers (UC) has a customer portal so that customers can manage their shipping. UC has several sharing rules in place and leverages the External Account Hierarchy to assist with data access. One of UC’s large customers, Cloud Kicks, has recently acquired Northern Trail Outfitters. Sales wants to merge these two accounts, but they are getting an error.

What could be the cause of the error?
A . Accounts with active Experience Cloud users cannot be merged with another account.
B. The user trying to merge the accounts does not have the Merge Portal Roles permission.
C. The user trying to merge the accounts does not have the System Administrator profile.
D. Accounts used in an External Account Hierarchy cannot be merged with another account.

Answer: D