When running basic MPLS in conjunction with VPNs, how many labels does each packet contain?

When running basic MPLS in conjunction with VPNs, how many labels does each packet contain?

A.
Each packet contains one label that identifies the VPN.

B.
Each packet contains at least two labels. One label identifies the path to the egress router and one that identifies the VPN.

C.
Each packet contains at least three labels. One label identifies the ingress router, one identifies the egress router and one identifies the path that will be taken.

D.
Each packet contains at least three labels. One label identifies the ingress router, one label identifies the path to the egress router, and one identifies the VPN.