What is the recommended approach to achieve this?

Universal Containers (UC) is planning on a production release with a large data volume to be migrated to Salesforce from a back-office system. The incoming data is constantly being updated in the back-office system. UC would like to keep the data synchronized in near real-time in Salesforce.

What is the recommended approach to achieve this?
A . Use Bulk API for a one-time migration and an Apex web service call-in for an incremental load.
B . Use Bulk API for a one-time migration and a SOAP API call-in for an incremental load.
C . Use SOAP API for a one-time migration and a REST API call-in for an incremental load.
D . Use Bulk API for a one-time migration and a Bulk API call-in for an incremental load.

Answer: A