How does MPLS VPN architecture allow for overlapping address space between customers?

How does MPLS VPN architecture allow for overlapping address space between customers?

A.
The addresses are kept unique by prefixing them with a route distinguisher.

B.
The addresses do not class because a separate routing process is used for each customer within the MPLS network.

C.
A separate PE router is provided for each customer.

D.
Customers have to use registered addresses, they cannot overlap.