What are two functions of a Network Services Orchestrator in an NFV environment? (Choose two.)
A. It operates at the resource-facing services layer and provides overall lifecycle management at the network service level.
B. It provides an API-based northbound interface for transparent integration with systems that operate at the resource-facing services layer.
C. It provides a standards-based southbound interface for transparent integration with systems that operate at the customer-facing services layer.
D. It provides a standards-based northbound interface for transparent integration with systems that operate at the customer-facing services layer.
E. It operates at the customer-facing services layer and provides the management interface for the virtual network devices.
