Which private VLAN can have only one VLAN and be a secondary VLAN that carries unidirectional traffic upstream from the hosts toward the promiscuous ports
and the gateway?

A.
isolated VLAN

B.
primary VLAN

C.
community VLAN

D.
promiscuous VLAN

Explanation:
Understanding Primary, Isolated, and Community Private VLANs Primary VLANs and the two types of secondary VLANs (isolated and community) have these
characteristics:
·Primary VLAN– The primary VLAN carries traffic from the promiscuous ports to the host ports, both isolated and community, and to other promiscuous ports.
·Isolated VLAN –An isolated VLAN is a secondary VLAN that carries unidirectional traffic upstream from the hosts toward the promiscuous ports. You can configure
multiple isolated VLANs in a private VLAN domain; all the traffic remains isolated within each one. Each isolated VLAN can have several isolated ports, and the
traffic from each isolated port also remains completely separate.
·Community VLAN–A community VLAN is a secondary VLAN that carries upstream traffic from the community ports to the promiscuous port and to other host ports
in the same community. You can configure multiple community VLANs in a private VLAN domain. The ports within one community can communicate, but these
ports cannot communicate with ports in any other community or isolated VLAN in the private VLAN.

http://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/configuration/guide/cli/C LIConfigurationGuide/PrivateVLANs.html