Which technology should be organization consider for the southbound interface?

An organization leverages a multivendor network to sell connectivity services using Layer 3 VPN and VPLS. Where possible, the organization wants to use common APIs across vendors, in order to automate the configuration of network services. Which technology should be organization consider for the southbound interface?
A. BGP-LS
B. OpFlex
C. OpenFlow
D. NETCONF
E. PCEP