Comprehensive and Detailed In-Depth Explanation:

The business system in EWM integration represents the source or target system (e.g., ERP) in the landscape. Option A ("It is connected to a logical system…") is correct because it links to a logical system via RFC, and warehouse requests store the business system for tracking, configured in SPRO: SCM Extended Warehouse Management > Interfaces > Define Business System. Option C ("It can be used to separate materials…") is correct as it differentiates stock origins in multi-system scenarios. Option B is incorrect because RFC parameters are defined separately, and option D is handled by document type mapping, not the business system itself.