Which IOS configuration command is required to configure a VLAN as a private VLAN?

Which IOS configuration command is required to configure a VLAN as a private VLAN?
A . switch(config-vlan)# private-vlan common
B . switch(config-vlan)# private-vlan private
C . switch(config-vlan)# private-vlan primary
D . switch(config-vlan)# private-vlan transparent

Answer: C