What integration strategy should an Architect recommend?

In order to avoid slowing down inbound call center sales agents, Universal Containers wants to de-duplicate Lead records against their 3rd-party MDM system after that the agent has served the record in Salesforce.

What integration strategy should an Architect recommend?
A . Outbound message to MDM with a callback to Salesforce to mark duplicate Leads.
B . Sync the MDM system to a custom object in Salesforce and execute a Lookup validation rule against the object.
C . Batch APEX process to de-duplicate all records first in Salesforce then against MDM, deleting the newest MDM record.
D . Use Out-of-the-Box Lead De-duplication Rules to checkagainst MD

Answer: A