A$.$ Virtual path identifier $($VPI$)$ and virtual circuit identifier $($VCI$)$

B$.$ Virtual path connection $($VPC$)$ and virtual path identifier $($VPI$)$

C$.$ Virtual channel connection $($VCC$)$ and virtual circuit identifier $($VCI$)$

D$.$ Virtual path connection $($VPC$)$ and virtual channel connection $($VCC$)$