A network is composed of several VRFs. It is required that VRF users VRF_A and VRF_B be able to route to and from VRF_C， which hosts shared services. However， traffic must not be allowed to flow between VRF_A and VRF_B. How can this be accomplished？（）
- Aroute redistribution
- Bimport and export using route descriptors
- Cimport and export using route targets
- DCisco MPLS Traffic Engineering